What is a dimensional divisor?

The number a carrier divides the box volume by to convert cubic inches or cubic centimetres into a billable weight. FedEx and UPS publish 139 for inches. USPS uses 166. Most metric rate cards use 5,000, and Canada Post uses 6,000. A negotiated contract can set a higher number, which lowers the billable weight.

Does dimensional weight apply to every package?

Applicability depends on the carrier, service and contract. USPS dimensional-weight rules apply to eligible services and parcels above the applicable volume threshold. The divisor alone does not determine the final charge; confirm measurement rounding, billing increments and minimums.

How do I lower my dimensional weight?

Ship in the smallest box that protects the product, use mailers for soft goods, and negotiate a higher divisor. If a 3PL ships for you, ask which divisor their rate card uses and whether the box library is right-sized.

Is freight billed the same way?

LTL freight uses the applicable NMFC item and classification rules, including density, handling, stowability and liability. Class is one input to the rate. The freight density calculator provides a scoped density-based estimate.

Free tool

Dimensional weight calculator

Carriers bill on whichever is higher: what a box weighs on a scale, or its dimensional weight (length × width × height divided by a divisor). Enter a box and compare scale weight with dimensional weight, using a carrier or contract divisor. Choose measurement rounding and billing-weight increments for an estimate in lb or kg.

Use the calculator How it is calculated

139FedEx and UPS published divisor
166USPS, over 1 cubic foot
5,000most metric rate cards
Freeno signup, in or cm

Calculator

Enter a box and a divisor

Pick the preset that matches your carrier, or type the divisor from your rate card. Results update as you type.

Package details

Box dimensions and what it weighs on a scale

Length in

Width in

Height in

Scale weight lb

Dimensional divisor

Set by your carrier or 3PL contract

Or enter the divisor from your rate card

Billing weight increment

In the selected weight unit: 1 for whole units, 0.5 for half units, or 0 for an unrounded comparison. Use your service or contract rule.

Round each dimension up to the next whole inch or centimetre

Default: whole-inch dimensions and 1 lb increments for a U.S. parcel estimate. Other services may use different rules.

Estimated billing weight

21 lb

Higher of dimensional and scale weight, rounded up in 1 lb steps. Check service minimums and exceptions.

Published standardThe divisor FedEx and UPS publish for domestic shipments.

Scale weight

3 lb

What the box weighs on a scale.

Dimensional weight

20.72 lb

12 × 12 × 20 ÷ 139 = 20.72 lb

Try it: change the length to 30. Dimensional weight jumps and billable weight follows it. That is why bulky, light products cost more to ship than the scale suggests.

How it is calculated

Three steps, one number

Dimensional weight exists because a truck fills up by volume long before it hits its weight limit. Light, bulky boxes take space the carrier could sell to someone else.

Measure and multiplyLength × width × height of the box, in inches or centimetres. A 12 × 12 × 20 in box is 2,880 cubic inches.
Divide by the carrier divisor2,880 ÷ 139 (the FedEx and UPS published divisor) is 20.72 lb. In metric, 30 × 30 × 50 cm ÷ 5,000 is 9 kg.
Compare with the scale weightCompare the greater of scale and dimensional weight, then apply the service billing increment. A 3 lb box with raw dimensional weight of 20.72 lb becomes a 21 lb estimate using whole-pound rounding.

Measurement and weight rounding matter. Source: UPS dimensions and weight guidance. Reviewed October 24, 2026. Presets are examples; use the current rules for your exact service and contract.

Where the money goes. A 12 × 12 × 20 in box holding 3 lb has raw dimensional weights of 20.72 lb on divisor 139, 17.35 lb on 166, and 11.52 lb on 250. With one-pound billing increments, the estimates are 21, 18 and 12 lb, subject to service rules. The divisor and the box are the two levers you control.

Divisors by carrier

Published divisors, and what contracts do to them

Retail and daily rates use the published number. Contracts and 3PL rate cards set their own, and a higher divisor means a lower bill.

Dimensional divisors by carrier
Carrier	Inches (lb)	Centimetres (kg)	Notes
FedEx	139	5,000	Common U.S. parcel example. Confirm the service guide, rounding, minimums and contract exceptions.
UPS	139	5,000	U.S. daily-rate parcel example. Confirm service rules and contract exceptions.
USPS	166	Use U.S. service rules	Applies once a package is over 1 cubic foot (1,728 cubic inches).
DHL Express	139	5,000	International express. Metric divisor on most rate cards.
Canada Post	n/a	6,000	Domestic and cross-border, volumetric equivalent in kilograms.
Contracts and 3PLs	166 to 400	6,000+	Divisor is set in the contract. Higher is better for bulky, light products.

Published figures as of 2026. Check your own rate card or invoice, since surcharges, minimums and oversize rules change by service.

Lower the bill

Two levers: the box and the divisor

Both are within reach. One is a packaging decision, the other is a line in a contract.

Right-size the boxEvery inch of empty space is billable. Move to a box that fits, or a poly mailer for soft goods, and dimensional weight drops with the volume.Try a smaller box in the calculator
Negotiate the divisorThe divisor is a contract term like any other. Mid-volume shippers commonly negotiate 166 to 200, and large 3PLs pass through 250 and up.How to negotiate 3PL rates
Check what you pay nowPut your current fees into the rate checker and see whether dimensional weight is where the money goes at your volume.Open the rate checker

Questions

Dimensional weight, answered

What is a dimensional divisor?: The number a carrier divides the box volume by to convert cubic inches or cubic centimetres into a billable weight. FedEx and UPS publish 139 for inches. USPS uses 166. Most metric rate cards use 5,000, and Canada Post uses 6,000. A negotiated contract can set a higher number, which lowers the billable weight.
Does dimensional weight apply to every package?: Applicability depends on the carrier, service and contract. USPS dimensional-weight rules apply to eligible services and parcels above the applicable volume threshold. The divisor alone does not determine the final charge; confirm measurement rounding, billing increments and minimums.
How do I lower my dimensional weight?: Ship in the smallest box that protects the product, use mailers for soft goods, and negotiate a higher divisor. If a 3PL ships for you, ask which divisor their rate card uses and whether the box library is right-sized.
Is freight billed the same way?: LTL freight uses the applicable NMFC item and classification rules, including density, handling, stowability and liability. Class is one input to the rate. The freight density calculator provides a scoped density-based estimate.

Paying dim weight on every order?

A 3PL with a negotiated divisor can cut the shipping line without touching the product

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Dimensional weight calculator

Enter a box and a divisor

Package details

Dimensional divisor

Three steps, one number

Published divisors, and what contracts do to them

Two levers: the box and the divisor

Dimensional weight, answered

A 3PL with a negotiated divisor can cut the shipping line without touching the product

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Dimensional weight calculator

Enter a box and a divisor

Package details

Dimensional divisor

Three steps, one number

Published divisors, and what contracts do to them

Two levers: the box and the divisor

Dimensional weight, answered

Related tools and guides

A 3PL with a negotiated divisor can cut the shipping line without touching the product

Ready to shortlist 3PLs?

The 3PL newsletter, every two weeks

For brands

For 3PLs

3PLs by channel

3PLs by industry

Company