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DimCheck

Box Size Optimizer

Enter your current box and actual weight. DimCheck finds smaller dimensions that reduce billable weight — every candidate is rechecked through the same carrier rules, so the numbers match what carriers compute.

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Units

Minimum product dimensions (optional)

The smallest box your product and protective packaging can physically fit in.

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What this means

Carriers bill the greater of your package's actual weight and its dimensional (DIM) weight. If DIM weight is higher, every cubic inch of extra box is extra billed weight. Shrinking a box from 24 × 18 × 12 in to 20 × 16 × 10 in cuts billable weight from 38 lb to 24 lb under FedEx and UPS Daily rules — a 37% drop — before changing anything about the product itself.

Relevant rules

DIM weight = length × width × height ÷ divisor, after rounding each side per the carrier's published rule. FedEx and UPS Daily use a divisor of 139; UPS Retail and the industry-standard generic rule use 166; USPS uses 139 above one cubic foot; DHL Express uses 5,000 cm³/kg. See the full rule set with official sources on the carrier rules page.

Worked example

A 24 × 18 × 12 in box has a volume of 5,184 in³. Under FedEx rules: 5,184 ÷ 139 = 37.3, rounded up to 38 lb DIM weight. If the actual weight is 8 lb, the billable weight is 38 lb — a 375% increase driven entirely by the box. Reducing to 18 × 14 × 10 in (2,520 in³) gives 18.1 → 19 lb billable.

Potential action

Run this optimizer before ordering your next packaging run. Pick the smallest candidate that still fits your product plus protective packaging — the tool enforces your minimum product dimensions, but always confirm the physical fit yourself.