Multi-item packing estimator
Add the items you want to combine and the box you want to use. This estimates whether they will go in — and tells you plainly when it cannot be sure, rather than guessing.
What the three answers mean
- Likely fits. The estimator placed every piece in shelves and layers. Real packing is messier, so leave margin if it is tight.
- Will not fit. Proven by arithmetic, not by packing skill: either the items add up to more volume than the box holds, or one piece does not fit the box in any orientation even on its own. No arrangement can rescue either case.
- We cannot say. The estimator ran out of room, but the items do still fit by volume. A heuristic failing is not proof that no packing exists, so we will not tell you no. This is the honest middle, and it is a real answer.
How the estimator packs
- Every piece is grown by the spacing allowance you set.
- Pieces are sorted largest first, which is what "first-fit decreasing" means.
- They are placed into rows, rows into shelves, and shelves into layers — the way you would fill a box by hand, wall by wall.
- Each piece takes whichever allowed orientation keeps the layer shortest.
The same inputs always give the same answer. It is not an optimal solver, and it does not claim to be one — which is exactly why a failure is reported as "cannot say" rather than "no".
Worked example
Eight 4 × 4 × 4 in boxed mugs into a 12 × 12 × 12 in box.
- The mugs are 512 cu in in total; the box is 1,728 cu in.
- Two layers of four fit neatly, so the estimator places all eight.
- Add half an inch of spacing around each and every mug becomes 5 in, so a 2 × 2 × 2 arrangement needs only 10 in — still fine. At 5.5 in mugs it would not be.
Edge cases worth knowing
- Volume fitting is necessary, not sufficient. Items that add up to less than the box can still refuse to go in.
- Long thin items defeat shelf packing. They are exactly the case where a human beats the estimator, and where you will see "cannot say".
- Spacing applies to every piece. Half an inch around each of twenty items is a lot of volume.
- Fragile items need more than spacing. This models room, not protection. Use the material estimator for that.
Common questions
- Why will it not just say no?
- Because in most cases it does not know. Our estimator packs one particular way; a person can do better. Saying no would be claiming something we cannot prove, so we only say it when the arithmetic settles it.
- Is this the best possible arrangement?
- No. It is a good, deterministic first pass. Choosing and tuning the packing heuristic against real cases is still on our list.
- Can I mix different items?
- Yes — that is what this tool is for. For several copies of one item, the box size calculator searches arrangements more thoroughly.
- Does the order I list items in matter?
- No. Pieces are sorted by size before packing, so the same set always gives the same answer.