Carton Fill Calculator

Carton fill rate measures how much of a shipping box's total volume is actually used by the product units packed inside — calculated as total product volume divided by carton volume, expressed as a percentage. A low fill rate wastes freight space and can mean paying dimensional weight charges for mostly empty air.

Most operations target 80% or higher carton utilization for cost efficiency, though fragile or irregularly shaped products may need extra padding that lowers achievable fill rate. Comparing several carton sizes against your product's dimensions can reveal a better-fitting box that reduces wasted volume and shipping cost.

Example: packing 8 units of a 5 × 5 × 5 in product (125 in³ each, 1,000 in³ total) into a 20 × 20 × 20 in carton (8,000 in³) gives a fill rate of 12.5% (1,000 ÷ 8,000) — a sign the carton is too large for this quantity.

Fill rate by volume can flatter a pack that does not physically work. Eight 5-inch cubes occupy 1,000 cubic inches, but whether they fit a given carton depends on how they tile: a 10 × 10 × 10 in box holds them perfectly at 100% fill, while a 12 × 8 × 11 in box of similar volume cannot take them at all. Check the arrangement along each axis, not just the totals.

Void fill counts against you twice. Dunnage occupies volume the product could have used and adds material cost per parcel, so a carton at 40% product fill is paying for the box, the packaging that fills it, and the dimensional weight of the whole thing. Reducing carton size usually removes all three costs at once.

Compare fill against the dimensional weight threshold rather than an abstract target. What matters is whether the carton's dimensional weight exceeds its actual weight — if it does, you are billed on air, and the fix is a smaller box. If actual weight already exceeds dimensional weight, extra void space costs materials but not freight.

Case-pack quantity is the other half of the decision. Choosing a count that tiles cleanly into a standard carton, and that carton into a pallet layer, compounds savings through the whole chain: cartons that fit the pallet footprint without overhang reduce damage and avoid pallet-level oversize charges.

Fragile and irregular products have a genuine floor on fill rate, and forcing it higher can cost more in damages than it saves in freight. Treat 80% as a target for stable, boxy goods and set a lower realistic benchmark for items that need corner protection or suspension packaging.

This ignores void fill and dunnage volume — real fill is lower once bubble wrap or dividers are added.