A carton fit calculator is a quick way to reject obviously unsuitable boxes and compare regular arrangements. Its answer is only as useful as the packing model behind it. CartonMeter uses a deliberately transparent model: identical rectangular products arranged in a uniform grid.
Why test six orientations?
A rectangular product has three side lengths. Each can be aligned with a different carton axis, giving six possible permutations. The tool tests each permutation, counts how many padded items fit along each axis, and multiplies the three counts.
For a 40 × 30 × 20 cm inner carton and an 11 × 9 × 6 cm padded item, one orientation places 6 cm along the carton’s 40 cm side, 9 cm along its 30 cm side and 11 cm along its 20 cm side. That yields a 6 × 3 × 1 grid: 18 items. Decimal counts must be rounded down because a fraction of an item cannot occupy the last space.
What “best” means here
The result is the best of these six uniform layouts. It is not a proof of the largest possible number of items. Combining different orientations within a carton may improve the fit. Diagonal placement, nesting and flexible products require different models and are excluded.
Clearance applies around every item
The per-side allowance expands every item on all three axes. It does not simply shrink the carton once. That is useful when every unit has its own wrapping, but may be conservative when units share dividers. Enter a planning envelope that reflects the way your actual items will be packed.
Capacity is not a safety check
A box may geometrically hold many units yet exceed its intended load or a carrier’s weight limit. The tool has no product weights, carton strength ratings or load-bearing model. It also allows every rotation, which is unsuitable for items that must stay upright.
Product-volume utilization is the volume of the unpadded products divided by the carton’s internal volume. It excludes padding, so the remainder is not automatically empty air. A low figure can signal a layout worth investigating, but it does not prescribe how much cushioning to remove.
Turn the result into a trial pack
- Check the chosen orientation is permitted for the product.
- Lay out a sample using the real wrapping and inserts.
- Confirm the carton closes without forcing it.
- Weigh and measure the finished package.
- Check packaging and shipping requirements before dispatch.
Try the carton fit calculator and compare inner versus outer dimensions before moving to a shipping estimate.