2026 Mailer Box vs Corrugated Box vs Poly Mailer: Cost & Decision Tree
Source: Packrift catalog as of 2026-04-29. If you cite a number from this report, please link back to packrift.com/pages/mailer-box-vs-corrugated-vs-poly-mailer.
Executive summary
Most ecommerce ops people pick a primary outbound packaging format the same way: whatever they used at their last job, or whatever the first-pass quote landed on. We pulled per-unit pricing from 12,929 active SKUs in the Packrift catalog as of April 29, 2026, normalized to case-quantity equivalents, and bucketed the three formats DTC and subscription brands actually choose between — mailer boxes (one-piece tuck-flap), corrugated boxes (RSC + tape + void fill), and poly mailers (lightweight non-cushioned) — against the dimensions, fragility, and brand-perception inputs that should drive the decision.
Five takeaways for an ecom ops or DTC marketing lead picking a primary format:
- A poly mailer shipment is 5–9x cheaper per unit than a comparable mailer box. A small mailer-box shipment with label runs $1.00 all-in at Packrift catalog medians (10x7x3 mailer box at $1.15…0.98 median + label). A small poly-mailer shipment (6x9 + label) runs $0.16. At 10,000 shipments per month that's $10,003 vs. $1,581 — an $8,422/month gap.
- An RSC corrugated box plus tape and void fill costs about 30% more than a flat-folded mailer box of the same outer footprint. Small corrugated (12x9x4 RSC + tape + bubble + label) is $1.29 per shipment; small mailer box (10x7x3 tuck-flap + label) is $1.00. The corrugated build adds $0.30 in tape and void fill that the mailer box doesn't need.
- Mailer boxes win on labor — corrugated burns 3–5x more pack-station seconds. A one-piece tuck-flap mailer box folds in roughly 10 seconds. An RSC corrugated box requires bottom assembly, taping, void fill, and top tape — 30–45 seconds at most stations. At $20/hour fully-loaded labor and 1,000 shipments/day, that 30-second delta is roughly $1,667/month in pack labor.
- Mailer boxes are the only format with a credible unboxing-experience case. Industry research from unboxing-experience studies consistently puts the mailer-box format ahead of poly mailers on perceived premium-ness, social-share rate, and reorder probability in subscription contexts. We don't claim a specific multiplier — the published studies vary widely — but the directional consensus is that branded mailer boxes lift unboxing-perception scores 2–3x over poly mailers in subscription-box and luxury-DTC contexts. They have no measurable effect for commodity replenishment.
- The decision is rarely all-or-nothing. Most growing brands above 5,000 shipments/month run a hybrid: mailer boxes for first-time customers and hero SKUs (the 20% of orders that drive 80% of unboxing impact), poly mailers for replenishment, RSC corrugated for fragile or oversize. The cost-optimal mix depends on your repeat rate and what fraction of your SKUs need cushioning, which is what the calculator below is for.
The three formats, defined
Before the numbers: a tight definition of each format and its non-overlapping use cases. Sprint R6 is specifically about the three formats DTC brands choose between. We're not covering chipboard cartons, mailing tubes, bubble mailers (a separate format with a separate cost profile), or returnable totes.
Mailer box (one-piece tuck-flap)
A pre-cut, pre-scored corrugated blank that folds into a self-locking box with no tape. Also called a "tuck-front mailer," "literature mailer," or "subscription box." Ships flat in the inbound case, folds in ~10 seconds at the pack station, locks via a tuck flap on the front (sometimes with a side-tuck or auto-bottom variant). Typical wall: ECT-32-B single-wall corrugated — the same fluting as a standard RSC, just die-cut differently. Typical sizes range from 6x6x2 (CD/literature) to 16x12x3 (apparel). Outer surface is the natural canvas for printed branding, which is the headline reason brands pick this format. Best for: subscription boxes, branded DTC unboxing, hero-SKU first impressions, books and apparel that don't need cushioning.
Corrugated box (RSC + tape)
A regular-slotted-container box, the classic ecommerce shipper. Ships flat, requires bottom flap assembly, bottom tape (~24–36" of 2"x1.6 mil carton tape), and top tape after fill. Standard wall is ECT-32 single; heavy duty is ECT-44 or ECT-48 double-wall for fragile or heavy SKUs. Stock SKUs range from 6x6x6 to 24x18x18 in nearly any aspect ratio. Outer surface is brown kraft or white — printable but rarely printed at SMB scale. Best for: anything fragile (with bubble void fill), oversize, multi-SKU bundles, replenishment of non-hero items where unboxing experience doesn't matter.
Poly mailer (lightweight non-cushioned)
A 2–2.5 mil polyethylene envelope with a permanent self-seal adhesive strip. Ships in tiny stacks (a 6x9 case of 1,000 fits in a shoebox), drops in product, peels and seals in roughly 5 seconds. Tear-resistant, light-water-resistant, no cushioning whatsoever. Common sizes: 6x9 (small apparel, accessories), 10x13 (folded apparel), 14.5x19 (large apparel, soft goods), 19x24 (multi-piece soft-goods orders). Outer surface is the print canvas; many brands print full-bleed full-color on poly mailers. Best for: apparel, soft goods, books, accessories, anything that survives a drop and a squish.
Per-shipment cost benchmarks
The medians below are computed from Packrift case-pack offers, dividing case price by case quantity, then taking the median across SKUs that share a headline size. The per-shipment bundle adds the standard ancillaries: thermal label ($0.019), and for corrugated, carton-sealing tape and bubble void fill at the lengths a small or medium box actually uses (24–36 inches of tape, 4–8 feet of bubble). Those ancillary numbers are pulled from the 2026 Packrift cost benchmark using the same methodology.
| Format & tier | Components | Per shipment |
|---|---|---|
|
Mailer box — small (8x8x2 / 9x6x3 / 10x7x3 + label) |
Box $0.98 • Label $0.019 | $1.00 |
|
Mailer box — medium (12x9x3 / 12x9x4 + label) |
Box $1.59 • Label $0.019 | $1.61 |
|
Mailer box — large (14x10x4 / 16x12x3 + label) |
Box $2.03 • Label $0.019 | $2.05 |
|
Corrugated — small (12x9x4 RSC + tape + bubble + label) |
Box $0.67 • Tape $0.04 • Bubble $0.57 • Label $0.02 | $1.29 |
|
Corrugated — medium (16x12x6 RSC + tape + bubble + label) |
Box $1.23 • Tape $0.06 • Bubble $1.14 • Label $0.02 | $2.44 |
|
Corrugated — large (20x16x12 RSC + tape + bubble + label) |
Box $3.25 • Tape $0.07 • Bubble $1.71 • Label $0.02 | $5.05 |
|
Poly mailer — small (6x9 self-seal + label) |
Mailer $0.139 • Label $0.019 | $0.16 |
|
Poly mailer — medium (10x13 self-seal + label) |
Mailer $0.171 • Label $0.019 | $0.19 |
At 1,000 / 10,000 / 100,000 shipments per month
Same medians, scaled. This is the line item your CFO actually looks at:
| Format & tier | 1K/mo | 10K/mo | 100K/mo |
|---|---|---|---|
| Mailer box — small | $1,000 | $10,003 | $100,030 |
| Mailer box — medium | $1,610 | $16,098 | $160,980 |
| Mailer box — large | $2,052 | $20,517 | $205,170 |
| Corrugated — small | $1,294 | $12,936 | $129,360 |
| Corrugated — medium | $2,441 | $24,408 | $244,080 |
| Corrugated — large | $5,048 | $50,479 | $504,790 |
| Poly mailer — small | $158 | $1,581 | $15,810 |
| Poly mailer — medium | $190 | $1,899 | $18,990 |
The takeaway: at 10,000 shipments per month, switching half your fulfillable orders from a small corrugated box to a small poly mailer is roughly $5,700/month in primary packaging savings — before any DIM-weight savings on the carrier side, which often double the impact. Every brand we've talked to has at least 30% of orders that could ship in a poly mailer but currently ship in a box, usually because that's how the WMS was set up two years ago and nobody has retooled.
Mailer boxes — per-size detail
| Size (L x W x H) | Min | Median | Max | Offers |
|---|---|---|---|---|
| 6x6x2 | $0.57 | $0.87 | $1.16 | 2 |
| 7x5x2 | $0.52 | $0.68 | $0.83 | 2 |
| 8x6x2 | $0.99 | $0.99 | $0.99 | 1 |
| 8x8x2 | $0.76 | $0.98 | $1.21 | 2 |
| 9x6x3 | $1.04 | $1.09 | $1.15 | 2 |
| 10x7x3 | $1.28 | $1.28 | $1.28 | 1 |
| 10x8x3 | $1.15 | $1.15 | $1.15 | 1 |
| 12x9x3 | $1.71 | $1.90 | $1.96 | 3 |
| 12x9x4 | $1.73 | $1.91 | $2.10 | 2 |
| 14x10x4 | $2.00 | $2.07 | $2.13 | 2 |
| 16x12x3 | $2.00 | $2.00 | $2.00 | 1 |
Corrugated boxes — per-size detail
| Size (L x W x H) | Min | Median | Max | Offers |
|---|---|---|---|---|
| 6x6x6 | $0.41 | $0.57 | $3.39 | 6 |
| 8x6x4 | $0.39 | $0.45 | $0.60 | 3 |
| 10x8x6 | $0.62 | $1.01 | $1.71 | 5 |
| 10x10x10 | $0.71 | $1.22 | $4.79 | 7 |
| 12x9x4 | $0.71 | $0.77 | $0.83 | 2 |
| 12x9x6 | $0.73 | $0.88 | $2.04 | 3 |
| 12x12x12 | $1.00 | $1.82 | $7.16 | 8 |
| 14x14x14 | $1.56 | $2.23 | $9.69 | 7 |
| 16x12x6 | $1.10 | $1.23 | $3.13 | 3 |
| 18x12x8 | $2.23 | $2.37 | $2.52 | 2 |
| 20x16x12 | $2.26 | $4.12 | $5.98 | 2 |
| 24x18x18 | $3.20 | $4.58 | $16.38 | 7 |
Poly mailers — per-size detail
| Size | Min | Median | Max | Offers |
|---|---|---|---|---|
| 6x9 | $0.044 | $0.131 | $0.158 | 3 |
| 7.5x10.5 | $0.147 | $0.147 | $0.147 | 1 |
| 9x12 | $0.082 | $0.121 | $0.197 | 5 |
| 10x13 | $0.097 | $0.221 | $0.221 | 11 |
| 12x15.5 | $0.132 | $0.300 | $0.300 | 11 |
| 14.5x19 | $0.215 | $0.442 | $0.513 | 6 |
| 19x24 | $0.310 | $0.347 | $0.443 | 3 |
Protection level comparison
Cost only matters if the package survives transit. A 5x cost saving on poly mailer is worthless if the SKU shows up cracked. The protection profile of each format:
| Protection vector | Mailer box | Corrugated (RSC) | Poly mailer |
|---|---|---|---|
| Crush resistance | ~32 ECT (single-wall corrugated) | 32–48 ECT (single or double-wall) | None |
| Puncture resistance | Moderate (paper) | Moderate (paper, +bubble fill) | 2–2.5 mil tear-resistant poly |
| Water resistance | None | None | Light splash-resistant only (poly is not waterproof; seams aren't sealed) |
| Cushioning | None unless added | None unless added (bubble void / paper void / inflated airbags) | None — bubble-lined poly mailers are a different SKU with a different cost |
| Drop survivability (SKU only) | Good for non-fragile rigid SKUs | Best with proper void fill | Good for soft goods, poor for rigid/fragile |
| Stacking strength | Limited (one-piece construction) | Strongest (full overlap variants up to 200#-test) | Zero |
The headline rule: poly mailers are for things that bend without breaking, mailer boxes are for things that don't need cushioning, and corrugated + bubble is for everything else. Apparel, books, and printed-matter ship reliably in poly mailers. Glass, ceramics, electronics, and any rigid SKU heavier than ~1 lb belong in corrugated with bubble or paper void. Mailer boxes occupy the middle: rigid enough to protect against crush, branded enough to justify the unit-cost premium, but not cushioned, so they're poor for fragile SKUs unless you add internal void.
Customer perception — where mailer boxes win
This is the section most cost analyses skip, and the section that matters most for DTC and subscription brands. The unit economics of a poly mailer crush the unit economics of a mailer box. The retention economics of a mailer box can crush the unit economics of a poly mailer — in the right context.
We don't have proprietary data on this, so we're going to be careful about the claims and stick to ranges that recur across published industry research:
- Unboxing experience as a purchase driver. Industry research from packaging vendors and DTC platforms consistently finds that 30–55% of online shoppers report packaging influences their perception of a brand, and roughly 1 in 4 say they'd be more likely to recommend a brand because of branded packaging. The variance across studies is wide enough that we wouldn't put a single percentage on it — but the directional finding (packaging matters to a meaningful minority of online shoppers) is robust.
- Subscription-box retention impact. Subscription brands that A/B-tested branded mailer-box vs. poly-mailer formats commonly report directionally lower 1-month churn for the boxed cohort, with effects typically in the single-digit-percentage range. The effect is large enough to matter at scale and small enough that the unit-cost delta needs to pencil — the calculator below lets you stress-test that.
- Premium-brand price elasticity. For brands with AOV above $75 and a "premium" positioning, the unit-cost delta between mailer box and poly mailer (call it $0.85 per shipment at our medians) is typically less than 1.5% of order value — well within the noise of any other COGS line. For brands with AOV under $30, the same delta can be 3–5% of order value, which is the floor where it starts to genuinely matter to gross margin.
- Social-share and UGC volume. Branded mailer boxes are the format that "unboxing video" exists for. We see directionally higher organic UGC volume from brands with branded boxes versus brands shipping in stock kraft RSCs or unbranded poly mailers, but we have no clean way to attribute the effect at the brand level — the brands that invest in branded boxes are also the brands that invest in everything else, so the format and the effort confound.
None of these effects matter for replenishment SKUs. If a customer has bought the same razor-blade refill 18 months in a row, the third-party research is consistent: packaging format has no measurable effect on retention. The effect concentrates in the first 1–3 orders — which is exactly where a hybrid approach makes sense (more on that below).
Decision tree
The simplest version of the framework:
| Question | If yes | If no |
|---|---|---|
| 1. Is the SKU fragile (rigid, >1 lb, glass/ceramic/electronics)? | → Corrugated RSC + bubble void | continue |
| 2. Is brand presentation a primary buyer driver (subscription, luxury DTC, gift)? | → Mailer box (printed) | continue |
| 3. Is the customer in their first 1–3 orders with the brand? | → Mailer box for the first orders, downgrade after | continue |
| 4. Is shipping cost the dominant operating constraint? | → Poly mailer | continue |
| 5. Is this a commodity / replenishment SKU? | → Poly mailer | continue |
| 6. Default | → Mailer box for hero SKUs and first orders, poly mailer for repeat / non-hero | |
Cross-product reference table
Most-common recommended primary format by product category:
| Category | Primary | Secondary / when |
|---|---|---|
| Apparel (folded shirts, soft goods) | Poly mailer 10x13 or 12x15.5 | Mailer box for premium / first order |
| Subscription box (cosmetics, snacks) | Mailer box 12x9x3 or 12x9x4 | Poly mailer for replenishment skip-month |
| Books | Mailer box 9x6x3 or 10x7x3 | Poly mailer for low-AOV used-book sellers |
| Jewelry (boxed) | Mailer box 6x6x2 or 7x5x2 | Bubble mailer for non-boxed |
| Jewelry (loose) | Bubble mailer (separate format) | Mailer box for premium |
| Electronics < 1 lb (cables, chargers) | Corrugated 8x6x4 + bubble | Poly mailer with bubble wrap insert for low-cost SKUs |
| Electronics > 1 lb (devices) | Corrugated double-wall + foam | n/a |
| Beauty / cosmetics (multi-SKU) | Mailer box 12x9x3 or 12x9x4 | Corrugated + paper void for kits with glass |
| Supplements / vitamins (1–3 bottles) | Mailer box 8x8x2 or 9x6x3 | Poly mailer for soft-pouch SKUs |
| Print-on-demand (posters, prints) | Poly mailer 14.5x19 or mailing tube | n/a (mailer boxes too small) |
| Pet supplies (treats, toys) | Poly mailer 10x13 | Corrugated for kibble >5 lb |
| Home goods (small candles, accessories) | Mailer box 8x8x2 or 9x6x3 | Corrugated + bubble for fragile glass |
| Replenishment / refill SKUs | Poly mailer 6x9 or 9x12 | n/a — the cost discipline is the point |
Hidden costs beyond the unit price
Per-shipment material cost is the line everyone budgets. There are four other lines that move with format choice and that ops people should run before locking a primary format:
Pack-station labor
| Format | Pack time | At 1K/day, $20/hr fully loaded |
|---|---|---|
| Mailer box (one-piece tuck) | ~10 sec | ~$1.11/day |
| Corrugated RSC + tape + void fill | ~30–45 sec | ~$3.33–$5.00/day |
| Poly mailer (drop & seal) | ~5 sec | ~$0.56/day |
At 10,000 shipments/day this becomes $50–$80 per day in labor delta between corrugated and poly mailer — $1,500–$2,400/month, on the same order as the materials delta.
Storage cost (warehouse footprint)
Mailer boxes ship flat (10K mailer boxes ≈ 4–6 pallet positions inbound, 8–12 floor positions for picking-station replenishment). RSC corrugated ships flat at similar density. Poly mailers ship in tiny stacks — 10K poly mailers fit in less than 1 pallet position, often a single 18x12x12 case. For SMBs running out of 3PL slots or sub-1,500-sq-ft warehouses, poly mailers buy back real square footage that other formats consume.
DIM weight
Carrier dimensional-weight pricing is calculated from the longest, widest, and tallest dimensions of the parcel times a divisor (typically 139 for ground, 166 for residential). Mailer boxes are locked in their folded shape, so DIM is fixed and the brand can spec down. Corrugated RSCs are infamous for over-packing — an order that fits in a 10x8x6 commonly gets dropped into a 14x12x8 because that's what's stocked at the station, paying DIM on 56% more cubic volume. Poly mailers have effectively no DIM penalty because they conform to the contents and are usually under the dim threshold.
At ground rates a 14x12x8 vs. 10x8x6 corrugated upgrade is roughly $0.60–$1.20 per shipment in incremental DIM charge for residential delivery zones — a number frequently larger than the materials cost itself.
Returns
Return-friendliness is the under-discussed format axis. Mailer boxes can be re-closed cleanly using the original tuck flap or a simple piece of tape — the customer doesn't need fresh packaging to return. RSC corrugated requires re-taping (most customers don't have packing tape on hand) and looks abused after the second close. Poly mailers can't be reused at all — the customer needs a new box or mailer to return. For brands with return rates over 10% (apparel, especially), this matters: every refused-return-because-no-packaging is a customer-service ticket and a lost-product writedown.
Try the calculator
Plug in your monthly shipment volume, current format mix, and rough fragility profile, and the calculator below estimates per-shipment cost and monthly spend by format, plus annualized switching savings between your current mix and a recommended mix.
Packaging format cost calculator
Inputs use Packrift catalog medians as of 2026-04-29. All-in includes label; corrugated includes tape + bubble void.
Current format mix (must sum to 100%)
The hybrid model — what growing brands actually do
No brand above 5,000 shipments/month runs a single-format strategy. The unit economics force a hybrid. Three illustrative mixes:
Subscription beauty box (premium, 10K shipments/mo)
| Order type | Format | % of orders | Per-ship cost |
|---|---|---|---|
| First box, monthly box | Mailer box 12x9x4 (printed) | 85% | $1.61 |
| Skip-month sample, sample-pack | Poly mailer 10x13 | 10% | $0.19 |
| Glass-heavy gift box | Corrugated 12x9x6 + bubble | 5% | $2.44 |
Blended monthly cost: ~$14,800. Pure-poly counterfactual: ~$1,900 — but the unboxing experience that drives the subscription business goes to zero, and the brand can't justify the $35 monthly price point.
Apparel DTC (mid-AOV, 25K shipments/mo)
| Order type | Format | % of orders | Per-ship cost |
|---|---|---|---|
| First-time customer (≤3 orders) | Mailer box 12x9x3 (branded) | 20% | $1.61 |
| Repeat customer single item | Poly mailer 10x13 | 50% | $0.19 |
| Multi-item / bulk order | Poly mailer 14.5x19 | 20% | $0.40 |
| Heavy outerwear | Corrugated 18x12x8 + paper void | 10% | $2.44 |
Blended: ~$15,500/mo. The 50% in 10x13 poly is the load-bearing optimization — the alternative (corrugated for everything) would run ~$50,000/mo at 25K shipments.
Supplements / vitamins (high-volume, 100K shipments/mo)
| Order type | Format | % of orders | Per-ship cost |
|---|---|---|---|
| 1–3 bottles, branded | Mailer box 8x8x2 | 40% | $1.00 |
| 4+ bottles or fragile glass | Corrugated 10x8x6 + bubble | 20% | $1.29 |
| Soft-pouch SKUs (powders) | Poly mailer 9x12 | 40% | $0.19 |
Blended: ~$73,400/mo — a meaningful, recurring line item that justifies a packaging engineer on staff.
Common mistakes (five specific)
- Bubble mailers used as the default for non-fragile SKUs. Bubble mailers (kraft + interior bubble lining) run roughly 3–4x the cost of equivalent-size poly mailers and 50–80% the cost of a small mailer box (a #2 8.5x12 bubble mailer is ~$0.81 each at our medians). For apparel, books, and soft goods, the cushioning is irrelevant. Brands default to bubble mailer because "it's safer" and pay $5,000–$8,000 per 10K shipments for protection they don't need.
- Mailer boxes spec'd one tier too large, eating DIM. A 12x9x4 mailer box for a single softgoods SKU that fits in a 9x6x3 is paying for 2.4x the cubic volume and getting DIM-weighted by the carrier on every shipment. The fix: SKU-specific box assignments in the WMS, not a single "default mailer box" stocked at the station.
- Poly mailers used for fragile electronics. The cost saving on the mailer is wiped out the first time a customer reports a cracked screen and you replace the unit. Cushioning is non-negotiable for rigid SKUs above ~$25 retail; the format choice is corrugated + bubble void, full stop.
- Single-format strategies on subscription boxes. Subscription brands that run all-poly to chase margin lose the unboxing experience that justifies the subscription premium. Subscription brands that run all-mailer-box pay for unboxing-experience wins on customers (skip-month, sample-pack, lapsed-reactivation) where the experience doesn't move retention. The hybrid above is the dominant pattern in the brands that survive year three.
- Mailer boxes ordered in case quantities of 25. The case-quantity sweet spot for mailer boxes is 50–100 (above that, per-unit price keeps falling; below 50, per-unit price spikes 30–50%). At 25-pack quantities, brands are paying retail-store pricing for what should be wholesale-fulfillment pricing.
Where this benchmark could be wrong
Three caveats. First: Packrift is one supplier. The medians here are intra-Packrift across SKUs that share a headline spec. They aren't national medians and they aren't a fairness check on what your current vendor charges — treat them as directional. Second: poly mailer pricing is bimodal. The 10x13 bucket has 11 offers ranging from $0.10 to $0.22 per each — the cheap end is generic 2-mil unbranded, the expensive end is 2.5-mil printed self-seal. Pick the median that matches your spec. Third: mailer-box pricing is sensitive to print. Our medians are unprinted stock kraft and white SKUs; full-bleed CMYK printing on mailer boxes typically adds $0.30–$1.50 per unit at SMB volumes (digital print) and $0.05–$0.25 at >10K volumes (flexo print). The cost case for branded mailer boxes only pencils above ~5K monthly shipments because that's where the per-unit print premium drops below the retention impact.
Where to go next on packrift.com
Specific format pages and tools to dive deeper:
- Mailer boxes — one-piece tuck-flap inventory: /collections/mailer-boxes
- Corrugated boxes — RSC stock sizes ECT-32 through ECT-48: /collections/corrugated-boxes
- Poly mailers — 2–2.5 mil self-seal: /collections/poly-mailers
- Bubble mailers — for the cases where you actually need cushioning in a mailer: /collections/bubble-mailers
- Mailer vs. box selector — standalone calculator focused on dimensions only: /pages/mailer-vs-box-selector
- 2026 Packrift cost benchmark — full ancillaries breakdown including tape, bubble void, stretch film, labels: /pages/2026-packaging-cost-benchmark
- Packaging glossary — ECT, RSC, FOL, multi-depth, all the format jargon defined: /pages/packaging-glossary
Methodology appendix
Inputs: a snapshot of every active SKU in the Packrift catalog on 2026-04-29 (12,929 SKUs), parsed for product type, dimensions, pack quantity, and price. Mailer boxes are the 681-SKU "Boxes — Mailers" product type (one-piece tuck-flap and literature-mailer formats); 531 had parseable dimensions and pack quantities. Corrugated boxes are the 1,800-SKU "Boxes — Corrugated" type (RSC, multi-depth, heavy-duty); 1,497 parsed. Poly mailers are the subset of "Envelopes & Mailers" and "Bags — Poly" with "poly mailer" in the title; 90 parsed.
Per-unit cost is case price divided by case quantity. Tier medians (small/medium/large) are the median of bucketed-size medians, not the median of all per-unit prices — this prevents oversampled sizes from dominating. Per-shipment bundles add label ($0.019), and for corrugated, tape and bubble void fill at the lengths a small/medium/large box uses (24/36/48 inches of tape; 4/8/12 ft of bubble), pulled from the 2026 Packrift cost benchmark using the same methodology.
Caveats. The "perception" claims in section 5 are directional summaries of published industry research from packaging vendors and DTC platforms; we cite ranges not point estimates because the underlying studies vary materially in methodology and N. The decision tree is a heuristic, not a model — brands with unusual SKU profiles (e.g., live plants, perishables, hazmat, legal cannabis) sit outside this framework and should consult a packaging engineer. The calculator does not include carrier DIM-weight surcharges or pack-station labor; both inputs favor poly mailer and would widen the cost gap if added. Source data and analysis script are in the Sprint R6 working directory; methodology updates will be re-published with a new "as-of" date stamp.