Will this fit in this box?
Enter your item and the inside of your box, and this tells you whether it fits, how much room is left on each side, and the smallest box that would work. It tests all six ways the item can be turned.
How this calculator works
- Your padding is added to both sides of each measurement, so a 12 in item with 0.5 in of padding needs 13 in of space.
- If the item can be turned, all six axis-aligned orientations are tested against the inside of the box.
- Any orientation where every measurement is less than or equal to the matching box measurement is a fit.
- The roomiest orientation is reported, along with the clearance left on each axis. A fit with 0.25 in or less on its tightest side is called out as barely fitting.
No carrier rule is involved, so there is no "last verified" date on this page. It is geometry, and it is the same in 2026 as it was in 1926.
Worked example
A 12 × 8 × 5 in item, a box measuring 14 × 10 × 6 in inside, and 0.5 in of padding on every side.
- Padding makes the item 13 × 9 × 6 in.
- Against the box that leaves 1 in, 1 in, and 0 in of clearance.
- It fits — but with nothing to spare on the height, so it is reported as barely fitting. There is no room for a packing slip laid flat on top.
Edge cases worth knowing
- Inside versus outside. A box listed as 14 × 10 × 6 is usually measured outside. Single-wall corrugate takes roughly an eighth of an inch per side; double-wall takes more.
- Rotation is not always physical. The calculator will happily turn a framed print on its corner. Uncheck rotation when orientation matters.
- Real boxes flex. Corrugated board bows outward under load and inward when taped. A clearance of zero on paper is often a struggle in practice.
- Irregular shapes. This treats your item as a rectangle. For something with a handle, a spout, or a curve, measure the widest point in each direction.
- Padding compresses. Bubble wrap and foam squash down under tape. Some tightness is recoverable; a negative clearance is not.
Common questions
- Should I use the inside or outside measurement of the box?
- Inside, always. Outside dimensions include the thickness of the cardboard, which is the difference between a fit and a repack.
- How much padding do I actually need?
- Half an inch per side suits most sturdy items. Two inches per side is the usual guidance for anything fragile, which means four inches added to each measurement.
- What does "barely" mean here?
- The tightest side has 0.25 in of clearance or less. It fits, but there is no margin for a squashed box, a thicker-than-expected wrap, or a packing slip.
- Does a smaller box always cost less to ship?
- Not always, but it often helps. Carriers bill on the greater of actual weight and dimensional weight, and dimensional weight comes straight from the box size. Check the dimensional weight calculator once you know which box you are using.
- Can it tell me if several items fit together?
- Not this one — it handles a single item. For multiple pieces in one box, use the multi-item packing estimator.