Large Flat Rate Box: Dimensions, Price and What Fits
The USPS Large Flat Rate Box is 12 x 11 3/4 x 5 1/2 inches inside, or 30.5 x 29.8 x 14.0 cm. It ships up to 70 lb to any US address for $36.10, and the box itself is free.
| Inside | 12 x 11 3/4 x 5 1/2 |
| Outside | 12 1/4 x 12 x 6 |
| Post Office price | $36.10 |
| Online postage | $32.75 |
| Weight limit | 70 lb |
| Spec | US | Metric |
|---|---|---|
| Size: inside | 12 x 11 3/4 x 5 1/2 in | 30.5 x 29.8 x 14.0 cm |
| Size: outside | 12 1/4 x 12 x 6 in | 31.1 x 30.5 x 15.2 cm |
| Inside volume | 776 cubic inches | 12.7 liters |
| Retail price | $36.10 | Post Office counter and kiosk, through January 16, 2027 |
| Commercial price | $32.75 | Click-N-Ship and other online postage |
| Weight limit | 70 lb | 31.8 kg |
| Delivery | 2 to 3 days | Priority Mail, not guaranteed |
| Included | Tracking and up to $100 insurance | On most shipments |
| Cost of the box | Free | Post Office lobby or usps.com |
Will it fit in a large flat rate box?
Enter the size of your packed item. The checker tests it against every flat rate box and names the cheapest one that fits.
Enter the three measurements of your packed item.
The checker turns your item to find the best way in and compares it with USPS inside dimensions. It does not allow for padding or bulging sides.
What fits in a large flat rate box
The Large Flat Rate Box suits small kitchen appliances, stacks of books, tools, shoes without the shoe box and care packages. The counts below come from the published inside dimensions and typical item sizes, packed in a simple grid with no padding, so treat them as the ceiling.
| Item | Typical size | How many fit |
|---|---|---|
| Mass-market paperback | 6.9 x 4.25 in, about 1 in thick | up to 12 |
| DVD case | 7.5 x 5.3 x 0.6 in | up to 20 |
| Blu-ray case | 6.75 x 5.3 x 0.5 in | up to 24 |
| CD jewel case | 5.6 x 4.9 x 0.4 in | up to 60 |
| Boxed deck of playing cards | about 3.6 x 2.6 x 0.7 in | up to 102 |
| Trade paperback | 9 x 6 in, about 1 in thick | up to 10 |
| Hardcover novel | about 9.5 x 6.5 x 1.5 in | up to 3 |
| Ream of letter paper, 500 sheets | 11 x 8.5 in, about 2 in thick | up to 2 |
| 12 oz beverage can | 2.6 in across, 4.83 in tall | up to 16 |
| 13 inch laptop | about 12 x 8.5 x 0.6 in | 1, exact fit with no room for padding |
What does not fit in a large flat rate box
| Item | Typical size | Use instead |
|---|---|---|
| 12 inch vinyl record in its jacket | 12.375 in square | Does not fit any flat rate box |
| Legal-size paper | 14 x 8.5 in | Does not fit any flat rate box |
| Men's shoe box | about 13 x 8 x 5 in | Does not fit any flat rate box |
USPS requires the flaps to close within their normal folds, so a box that bulges or needs extra tape to hold shut does not qualify for the flat rate price.
Large Flat Rate Box price in 2026
The Large Flat Rate Box costs $36.10 at a Post Office counter or kiosk and $32.75 at the commercial price you get with Click-N-Ship on usps.com and other online postage. The price is the same for every weight up to 70 lb and every US destination, and it includes the box.
| Period | Retail price | Why it changed |
|---|---|---|
| January 18 to April 25, 2026 | $31.50 | 2026 base price |
| April 26 to October 3, 2026 | $34.00 | Temporary transportation increase |
| October 4, 2026 to January 16, 2027 | $36.10 | Temporary holiday increase added |
| From January 17, 2027 | $31.50 | Both temporary increases end |
USPS has said prices return to their approved levels on January 17, 2027, which would bring the Large Flat Rate Box back to $31.50 unless a new price change is approved first. As of November 10, 2026, USPS had not announced one.
Large Flat Rate Box vs your own box
Flat rate is one price for any weight and distance. Your own box is priced by weight and zone, so it wins when the package is light or the trip is short. The tables use USPS retail prices effective October 4, 2026, against the $36.10 flat rate price.
The short answer: the Large Flat Rate Box is cheaper than Ground Advantage in every zone from 26 lb up. Ground Advantage in your own box is cheaper in every zone up to 8 lb. From 9 lb the flat rate box starts winning on long hauls: at 9 lb it is cheaper for zone 8 only. Against Priority Mail by weight, which is the same 2 to 3 day service, the flat rate box wins in every zone from 24 lb.
| Weight | Zone 1 | Zone 2 | Zone 3 | Zone 4 | Zone 5 | Zone 6 | Zone 7 | Zone 8 | Flat rate is cheaper |
|---|---|---|---|---|---|---|---|---|---|
| 5 lb | $13.75 | $14.35 | $15.35 | $16.60 | $18.85 | $21.00 | $23.80 | $27.45 | Never |
| 8 lb | $15.40 | $15.65 | $16.60 | $18.45 | $21.80 | $25.50 | $29.85 | $34.55 | Never |
| 10 lb | $16.75 | $17.10 | $18.05 | $20.20 | $24.25 | $28.90 | $34.70 | $40.85 | Zone 8 only |
| 12 lb | $18.70 | $19.10 | $19.90 | $22.55 | $28.15 | $34.00 | $41.40 | $49.25 | Zones 7 to 8 |
| 15 lb | $20.90 | $21.00 | $21.65 | $24.45 | $31.70 | $39.50 | $49.40 | $60.10 | Zones 6 to 8 |
| 20 lb | $24.00 | $24.20 | $25.70 | $28.55 | $37.90 | $47.00 | $58.25 | $72.15 | Zones 5 to 8 |
| 26 lb | $37.45 | $40.15 | $44.35 | $53.75 | $67.80 | $80.55 | $93.40 | $107.50 | Every zone |
| 30 lb | $41.15 | $44.45 | $49.30 | $60.45 | $76.30 | $90.65 | $104.80 | $120.30 | Every zone |
| 40 lb | $49.40 | $53.40 | $59.40 | $74.10 | $94.15 | $112.15 | $129.30 | $147.90 | Every zone |
| Weight | Zone 1 | Zone 4 | Zone 8 | Flat rate is cheaper |
|---|---|---|---|---|
| 5 lb | $15.10 | $18.30 | $39.00 | Zone 8 only |
| 8 lb | $17.05 | $20.50 | $53.80 | Zones 6 to 8 |
| 10 lb | $18.60 | $22.55 | $63.40 | Zones 6 to 8 |
| 12 lb | $20.75 | $25.05 | $75.60 | Zones 6 to 8 |
| 15 lb | $23.25 | $27.50 | $90.25 | Zones 5 to 8 |
| 20 lb | $26.80 | $32.35 | $113.70 | Zones 5 to 8 |
| 26 lb | $41.65 | $60.05 | $143.40 | Every zone |
| 30 lb | $45.85 | $67.55 | $155.30 | Every zone |
| 40 lb | $55.25 | $83.05 | $181.10 | Every zone |
Zone is set by the distance between the origin and destination ZIP Codes, from zone 1 for local to zone 8 for coast to coast. The USPS shipping calculator prices an exact package, and the Ground Advantage guide has the full rate table. Own-box prices here assume a package of 1 cubic foot or less with no side over 22 inches, which covers any box near flat rate size. Ground Advantage takes 2 to 5 business days, against 2 to 3 for Priority Mail.
Plain boxes close to this size
When the tables say your own box is cheaper, you need a plain box: USPS flat rate packaging can only ship at the flat rate price. These stock corrugated boxes are the nearest sizes. Measurements are inside dimensions.
Same length and half an inch more depth than the Large Flat Rate Box.
The box size chart lists every standard size, and the cheapest way to ship a package compares USPS, UPS and FedEx by weight.
Shipping light packages every day?A plain box and Ground Advantage usually beat flat rate under a few pounds. Stock the size you use most by the bundle.
Small vs Medium vs Large flat rate box
Footprints drawn to scale, inside length by inside width. Depth is not shown: Small 1 5/8 in, Medium 1 5 1/2 in, Medium 2 3 3/8 in, Large 5 1/2 in.
| Box | Inside size, in | Cubic inches | Retail price | Price per cubic inch |
|---|---|---|---|---|
| Small | 8 5/8 x 5 3/8 x 1 5/8 | 75 | $14.65 | 19.4¢ |
| Medium 1, top-loading | 11 x 8 1/2 x 5 1/2 | 514 | $25.80 | 5.0¢ |
| Medium 2, side-loading | 13 5/8 x 11 7/8 x 3 3/8 | 546 | $25.80 | 4.7¢ |
| Large | 12 x 11 3/4 x 5 1/2 | 776 | $36.10 | 4.7¢ |
Space in the Small box costs about 4 times as much per cubic inch as space in the Large box. The Medium and Large boxes cost nearly the same per cubic inch, so pick between them on fit, not on value.
Where to get large flat rate boxes free
USPS gives the Large Flat Rate Box away. Pick them up in a Post Office lobby, or order them from the Postal Store on usps.com as a single box, a pack of 10 or a pack of 25, all at $0.00. USPS mails the supplies to you at no charge by Ground Advantage. You pay only when you buy postage.
Rules for flat rate boxes
- Flat rate postage only. USPS states that Priority Mail Flat Rate supplies may only be used to ship via Priority Mail Flat Rate. They cannot go by Ground Advantage or Media Mail.
- 70 lb maximum. The price does not change with weight up to that limit.
- Flaps must close. The box has to close within its normal folds.
- No dimensional weight. Flat rate boxes are exempt from dimensional weight and nonstandard fees.
Frequently asked questions
What are the dimensions of a large flat rate box?
The Large Flat Rate Box is 12 x 11 3/4 x 5 1/2 inches inside and 12 1/4 x 12 x 6 inches outside. It holds about 776 cubic inches.
How much does a large flat rate box cost in 2026?
$36.10 at the Post Office and $32.75 with online postage such as Click-N-Ship, through January 16, 2027. USPS has said the retail price returns to $31.50 on January 17, 2027 unless a new price change is approved.
How big is a large flat rate box in cm?
The Large Flat Rate Box is 30.5 x 29.8 x 14.0 cm inside and 31.1 x 30.5 x 15.2 cm outside.
How much weight can a large flat rate box hold?
Up to 70 lb. The price is the same at any weight, as long as the flaps close within their normal folds.
Are large flat rate boxes free?
The box is free at Post Office locations and from the Postal Store on usps.com, in singles and packs of 10 or 25. You pay the $36.10 flat rate postage when you ship it.
Is a large flat rate box cheaper than Ground Advantage?
From 26 lb up it is cheaper in every zone at retail prices. Up to 8 lb, Ground Advantage in your own box costs less in every zone. In between, it depends on how far the package travels.
Can I use a large flat rate box for Ground Advantage or Media Mail?
No. USPS flat rate packaging may only be used for Priority Mail Flat Rate. For Ground Advantage or Media Mail, use a plain box.
Related guides
- Small Flat Rate Box
- Medium Flat Rate Box
- USPS flat rate box sizes and prices
- USPS shipping calculator
- USPS Priority Mail box sizes
- USPS Ground Advantage rates
- Cheapest way to ship a package
Dimensions and prices from USPS Notice 123, effective October 4, 2026, and the USPS Postal Store, checked November 10 and 11, 2026. Ground Advantage and Priority Mail prices are retail. Item sizes are typical; measure yours before you pack.