--- title: "What Is Dimensional Weight?" url: https://www.uncap.com/glossary/dimensional-weight author: "Denis Dyli" published: 2026-10-28 updated: 2026-10-28 summary: "Dimensional weight, or DIM weight, is a billing weight that parcel carriers calculate from a package's size rather than its scale weight. The carrier multiplies the package's length, width and height and divides the result by a divisor. When the dimensional weight is greater than the actual weight, the shipment is billed at the dimensional weight." --- # What Is Dimensional Weight? > Dimensional weight, or DIM weight, is a billing weight that parcel carriers calculate from a package's size rather than its scale weight. The carrier multiplies the package's length, width and height and divides the result by a divisor. When the dimensional weight is greater than the actual weight, the shipment is billed at the dimensional weight. **Dimensional weight**: Dimensional weight, or DIM weight, is a billing weight that parcel carriers calculate from a package's size rather than its scale weight. The carrier multiplies the package's length, width and height and divides the result by a divisor. When the dimensional weight is greater than the actual weight, the shipment is billed at the dimensional weight. ## How it works FedEx describes dim weight as the amount of space a package occupies in relation to its actual weight, and UPS uses dimensional weight to calculate shipping costs when a package is large relative to its weight. The calculation: - Measure. Measure the package's length, width and height in inches. FedEx says to round each measurement to the nearest whole inch. - Multiply. Length x width x height gives the package's cubic size in inches. - Divide. Divide the cubic size by the carrier's divisor, also called the DIM factor, to get the dimensional weight in pounds. UPS says to increase any fraction to the next whole pound. - Compare. FedEx charges based on the dimensional weight or the actual weight of the package, whichever is greater. Divisors are set by each carrier and can change, so check the carrier's own page before you quote. As fetched on October 28, 2026: - FedEx: divide by 139 for U.S., Puerto Rico, and international shipments. - UPS: the divisor varies by rate type: 139 for Daily Rates and 166 for Retail Rates. Shopify notes that dimensional weight applies to some shipping services when a package's length x width x height exceeds 1 cubic foot (1,728 cubic inches), and that calculations vary between carriers. ## Common problems - Inside dimensions. Advertised box dimensions might refer to the inside of the packaging. Shopify says to measure and use the outside dimensions, because the outside dimensions are used to calculate the shipping cost. - One box for every order. In Shopify, a package assigned to a product variant overrides the store default package only for single item orders. Unless your products have a packed product size, orders with multiple items are rated with the store default package. - Oversized packaging. FedEx says dim weight pricing may reduce shipping costs for customers who pack more efficiently, and that oversized boxes packed with extra cushioning mean people are, in some cases, paying to ship air. ## Example A distributor ships a carton that measures 24 x 18 x 12 inches and weighs 20 pounds. - Cubic size: 24 x 18 x 12 = 5,184 cubic inches - At a 139 divisor: 5,184 / 139 = 37.29, rounded up to 38 pounds - At a 166 divisor: 5,184 / 166 = 31.23, rounded up to 32 pounds Either way, the carton is billed above its 20 pound scale weight. Packed in a 20 x 16 x 10 inch carton instead, the cubic size is 3,200 cubic inches, and 3,200 / 139 = 23.02, rounded up to 24 pounds. ## On Shopify Shopify sends your default package dimensions to your shipping carrier along with your order's weight to calculate shipping rates for your customer. If the dimensional weight is larger than the order's weight, the customer is charged for the dimensional weight. - Store default package. It sets the shipping rate at checkout when you use weight-based or carrier-calculated rates, for products and variants that don't have a package assigned. - Packed product size. You can add the outer length, width and height of a product after it's packed. Items in each shipment are then packed into the smallest of your saved boxes that fits them, so customers pay a rate closer to what your carrier charges you for the label. ## How Uncap helps Uncap's guide to [shipping in Shopify B2B commerce](/post/shipping-the-most-underrated-growth-driver-in-shopify-b2b-commerce) is blunt about it: poor packaging data inflates costs or eats margins, so set accurate dimensions for every SKU. Uncap's [corrugated boxes page](/industry/corrugated-boxes) describes a fits-inside finder, built during implementation from your size table: the buyer enters the product's dimensions and sees the boxes whose inside dimensions clear them, smallest first, so the box that fits is also the one that keeps dimensional weight down. ## Related terms - LTL freight - Freight class - Hundredweight - Landed cost - Order fulfillment ## Sources - FedEx: What is dimensional weight? - UPS: Package dimensions, size limits and weight guide - Shopify Help Center: Understanding shipment packaging and weights ## Frequently asked questions ### What is dimensional weight vs actual weight? Actual weight is what the package weighs on a scale. Dimensional weight is calculated from its size: length x width x height in inches, divided by the carrier's divisor. FedEx charges whichever of the two is greater. ### What is dim divisor? The dim divisor, which UPS also calls the DIM factor, is the number a carrier divides a package's cubic inches by to get its dimensional weight in pounds. On October 28, 2026, FedEx listed 139 for U.S., Puerto Rico, and international shipments, and UPS listed 139 for Daily Rates and 166 for Retail Rates. ### Does UPS charge dimensional weight or actual weight? UPS uses dimensional weight to calculate shipping costs when a package is large relative to its weight, and says dimensional weight may apply to all UPS domestic and international package services. UPS's Rate and Service Guide sets out how it determines the billable weight.