Enter dimensions.
Get the right box.
Stop buying boxes that are too big, too small, or wrong for your item. Enter what you're shipping and get matched to real corrugated box sizes from real suppliers.
BOX FINDER
Enter your item's outer dimensions. We add padding and find the best-fitting boxes.
Enter your item dimensions
and hit Find.
HOW IT WORKS
Measure your item
Measure the actual item at its longest, widest, and tallest points. If it's irregularly shaped, measure the bounding box — the smallest rectangle that contains it.
Choose your padding
Standard items need 1 inch of padding on each side. Fragile items (glass, electronics, ceramics) need 2–3 inches for adequate void fill protection.
Get matched boxes
We search our box database for every size that fits, sorted by how little wasted space they have. Tightest fit first — you don't want a box that's 60% air.
Buy from any supplier
Each result links to The Boxery, Uline, and Amazon. Prices vary — check all three. Boxery and Uline often win on volume; Amazon on single-box convenience.
COMMON SIZING MISTAKES
Too much air space
A box that's significantly larger than your item requires more void fill, costs more to ship (dimensional weight), and gives your item room to shift and get damaged. Aim for 1–2 inches of padding, no more than needed.
Reusing old boxes
Used boxes lose up to 50% of their stacking strength after one use. Carriers may reject severely worn boxes, and water damage or previous crushing can cause in-transit failure even if the box looks fine externally.
Wrong wall strength
Standard 32 ECT boxes hold 65 lbs. Items over 50 lbs, or fragile goods that need stacking protection, need 200–275 ECT double-wall construction. The box type matters as much as the size.
Ignoring DIM weight
UPS and FedEx charge by dimensional weight for large, light packages. A 24×24×24 box weighing 5 lbs ships at 100 lbs DIM weight (÷139). Our results show you the DIM weight so you can choose accordingly.
MOST-SEARCHED BOX SIZES
Click any size to pre-fill the finder.
FAQ
ECT measures how much edge pressure a corrugated box can withstand before buckling — it's the relevant strength rating for shipping. Standard single-wall boxes are 32 ECT (handles up to 65 lbs). Double-wall boxes are 200–275 ECT for heavier or fragile items. The old "burst test" (Mullen) is largely obsolete — carriers and retailers have moved to ECT as the standard.
Measure the bounding box — the smallest rectangular box that could contain your item. For an L-shaped object, measure the longest overall dimension in each direction, not the individual legs. For a sphere, measure the diameter as length, width, and height. When in doubt, go slightly larger — an extra inch of void fill is cheaper than a damaged shipment.
It depends on quantity and urgency:
- Uline: Best pricing on large orders (100+ boxes), consistent quality, reliable stock.
- The Boxery: Competitive on medium quantities (25–99 boxes), often cheaper per unit than Amazon for single box types.
- Amazon: Best for low quantities (1–25 boxes), fast delivery, convenient if you already buy supplies there.
All three are legitimate suppliers — check price per box for your quantity before ordering.
UPS, FedEx, and DHL charge by the greater of actual weight or dimensional weight. DIM weight = (L × W × H) ÷ 139 for UPS/FedEx. A 20×20×20 box is 57.5 lbs DIM — you pay for 57.5 lbs even if the item weighs 3 lbs. USPS only applies DIM weight to packages over 1 cubic foot. For large, light items, choosing a smaller box can significantly reduce shipping costs.
For USPS flat rate boxes: yes, but you must use Priority Mail flat rate — you can't use these boxes with regular Priority or Ground rates. For FedEx/UPS free boxes: they must be used with that carrier's service and can't be repurposed for other carriers. Free carrier boxes are a great deal when your item fits and the flat rate is competitive, but you're locked into that carrier's rates.
A useful rule: your item should not move more than ½ inch in any direction inside the closed box. Test by gently shaking the packed box — if you hear or feel movement, add more fill. For fragile items, 2 inches of bubble wrap on all six sides is the minimum. Packing peanuts work well for irregularly shaped items; kraft paper works well for sturdy items that just need a snug fit.