Shipping Box Size Chart: Standard Sizes and How to Choose
This page is for ecommerce shippers picking standard cartons: you know roughly what you ship, and you want a stock size that fits it without paying to ship air. The chart below covers common shipping box sizes from our corrugated line, listed by inside dimensions, with a note on what each size handles well. Below the chart: how to measure a box, how to choose between two sizes, and what the strength rating on each product means.
Standard shipping box sizes at a glance
All dimensions are inside dimensions in inches, listed length x width x height. Every box in this chart is 32 ECT kraft corrugated, the common single-wall grade for parcel shipping. This chart focuses on mid-size and larger cartons; the dimension index linked below covers every size we stock.
This chart is the curated shortlist, not the whole wall. The box sizes by dimension index is the complete list of every size we stock, sorted by dimension, and the corrugated boxes collection covers the specialty formats as well: double wall, multi-depth, telescoping, side loading, and wardrobe boxes.
How to measure a box
Box dimensions are always inside dimensions, listed as length x width x height. Length is the longest side of the box opening, width is the shorter side of the opening, and height is the distance from the opening down to the base. Longest side first, every time. A 24x20x12 carton opens on a 24 by 20 inch face and is 12 inches deep.
Sizes are quoted inside the box because that is the space your product actually gets. The outside runs slightly larger than the listed size because of the thickness of the corrugated board, which matters when you are fitting cartons to shelf openings or building a tight pallet pattern. When you measure your product, put its longest side first too, so you are comparing like with like against the chart.
How to pick a size
- Go snug, not roomy. Pick the smallest box that holds the item plus its padding. A half-empty carton needs void fill, crushes more easily under stacking, and costs more to ship. Contents that cannot shift arrive in better shape than contents floating in a big box.
- Use the 2 inch rule for fragile items. Fragile goods want about 2 inches of cushioning on every side. In practice, add roughly 4 inches to each dimension of the item and step up to the closest stock size from there.
- Watch dimensional weight. Parcel carriers bill by dimensional weight when a box is large and light, so going one size up can raise your billed weight even though nothing else changed. Run your candidate size through the dimensional weight calculator before you commit, especially on large, light items.
If you are stuck between two sizes, or you are boxing an odd shaped product, work through what size box do I need. It walks from product dimensions to a specific carton, including the padding math.
Box strength basics
32 ECT is the common single-wall strength for parcel shipping, and every size in the chart above is 32 ECT kraft. ECT stands for edge crush test, a measure of stacking strength. For typical ecommerce loads, 32 ECT does the job without adding board weight you do not need.
Step up in strength when the load is heavy or dense, when cartons are stacked high in storage, or when a box has to survive more than one trip. The corrugated line also includes ECT-44 heavy-duty singles, ECT-48 double wall, and triple wall boxes at the extreme end. For how ECT ratings compare with the older 200 lb burst test standard, and which rating to buy by, see the 32 ECT vs 200 lb test guide.
Buying cartons in bulk and comparing suppliers on price and lead time? The best Uline alternatives page covers how we and the other bulk suppliers compare on box orders. For the rest of the packaging guides, start at the guides hub.
FAQ
Are shipping box dimensions inside or outside measurements?
Box dimensions are inside measurements. A box listed as 24x20x12 gives you 24 inches of usable length, 20 inches of width, and 12 inches of height. The outside runs slightly larger because of the thickness of the corrugated board, which matters if you are fitting boxes onto shelving or into a pallet pattern.
What order are box dimensions listed in?
Length by width by height, with length being the longest side of the box opening. A 36x12x12 box opens on the 36 by 12 inch face. This convention is standard across the packaging industry, so the first number is always the longest side of the opening.
What box strength do I need for normal parcel shipping?
32 ECT single-wall corrugated is the common standard for parcel shipping and covers most ecommerce products. Step up to ECT-44, ECT-48 double wall, or triple wall when contents are heavy or dense, when boxes get stacked high in storage, or when the same carton is reused across trips.
How much room should I leave for cushioning?
For fragile items, leave about 2 inches of space on every side for cushioning, which means adding roughly 4 inches to each dimension of the item before picking a box. For durable goods, a snug fit with minimal void fill protects better than a loose box, because contents that cannot shift do not build momentum in transit.
What if no standard size fits my product?
Start with the complete dimension index, since the chart on this page is only a shortlist. If the item height varies from order to order, multi-depth boxes with scored sides and two-piece telescoping boxes adjust to the load, and both are stocked in the corrugated line.