Carriers like UPS, FedEx, USPS, and DHL don’t just charge by how much your package weighs — they charge by how much space it takes up. Dimensional weight (DIM weight) is the pricing formula that turns a package’s size into a “billable weight.” If your box is large but light, you’re almost always billed on the dimensional weight, not the actual weight. Use the free calculator below to see exactly what you’ll be charged for.
Free Dimensional Weight Calculator
How dimensional weight is calculated
The formula is simple: (Length × Width × Height) ÷ DIM divisor = dimensional weight. The divisor depends on the carrier and rate type. For US domestic UPS and FedEx daily rates the divisor is 139; for many USPS and retail rates it’s 166; international air shipments commonly use a metric divisor of 5000 or 6000 (cm³ per kg).
Your billable weight is the greater of the actual weight and the dimensional weight. That’s the number the carrier prices your shipment on — which is why oversized, under-packed boxes quietly inflate shipping costs.
How to lower your dimensional weight costs
- Right-size your packaging. Every unused inch is space you’re paying to ship. Match box size to the product.
- Use poly mailers where safe. Non-boxed shipments often avoid DIM pricing entirely.
- Negotiate your divisor. High-volume shippers and 3PLs can secure a more favorable DIM divisor, directly lowering billable weight.
- Consolidate zones. Shipping from a fulfillment center closer to your customers reduces zones and cost per package.
A 3PL with pre-negotiated carrier rates and right-sized packaging can meaningfully cut what you pay per order. Talk to Shipo about lowering your blended shipping cost.