--- title: "What Is a Unit of Measure (UOM)?" url: https://www.uncap.com/glossary/unit-of-measure author: "Denis Dyli" published: 2026-10-28 updated: 2026-10-28 summary: "In B2B inventory and ordering, a unit of measure (UOM) is the unit in which an item is counted, stocked, bought, priced or sold, such as each, box, case, pallet, pound or foot. One item often has several: a base unit of measure for inventory and alternate units for purchasing and sales, linked by a conversion quantity." --- # What Is a Unit of Measure (UOM)? > In B2B inventory and ordering, a unit of measure (UOM) is the unit in which an item is counted, stocked, bought, priced or sold, such as each, box, case, pallet, pound or foot. One item often has several: a base unit of measure for inventory and alternate units for purchasing and sales, linked by a conversion quantity. **Unit of measure**: In B2B inventory and ordering, a unit of measure (UOM) is the unit in which an item is counted, stocked, bought, priced or sold, such as each, box, case, pallet, pound or foot. One item often has several: a base unit of measure for inventory and alternate units for purchasing and sales, linked by a conversion quantity. ## How it works A unit of measure (UOM) in an ERP or inventory system tells everyone what one unit of an item means. Microsoft's documentation for Dynamics 365 Business Central describes the common setup: each item gets a base unit of measure, which defines how the item is stored in inventory and is the basis for conversion to alternate units of measure. - Base unit of measure: the unit inventory is kept in. - Alternate units of measure: units assigned to purchase, production or sales documents to specify how many units of the base unit of measure you handle at a time. Microsoft's example is buying an item on pallets and using single pieces in production. - Conversion quantity: in Business Central, the Qty. per Unit of Measure field holds how many units of the base unit of measure the alternate unit contains. ## Base vs. alternate units of measure Every alternate unit converts back to the base unit: - Quantity in base units = quantity ordered x quantity per unit of measure - Price per base unit = price per alternate unit / quantity per unit of measure That is how one item can be bought by the pallet and sold by the case while its inventory is kept in one base unit, such as each. ## Common problems - Rounding: Microsoft notes that converting alternate units back to the base unit can lead to rounding issues. Its example is a box of six pieces where one piece is missing: receiving five of six pieces would post 4.99998 pieces unless a quantity rounding precision is set. - Mismatched units between systems: a unit of measure that means each in one system and case in another makes an inventory sync drift. - Ordering in the wrong unit: a store that defaults to the smallest orderable unit makes buyers calculate the quantity themselves. ## Example A distributor stocks a fastener in eaches and buys it in cases of 12. - Order: a buyer orders 5 cases, which is 5 x 12 = 60 eaches in inventory. - Price: a case sells for $30.00, so the price per each is $30.00 / 12 = $2.50. - Pallet: if a pallet holds 80 cases, one pallet is 80 x 12 = 960 eaches. ## On Shopify Shopify B2B quantity rules control how many of an item a buyer can order at one time. If you want to sell a product in certain increments, you can use increment quantity rules: if your products are boxed in multiples of 10, you can set the increment rule to 10. Minimum and maximum quantity rules set the fewest and greatest number of an item that can be purchased at one time, and, as of October 28, 2026, Shopify says you can add up to 10 volume price breaks per product. Shopify can also display a unit price: if you sell products in quantities or measurements, you can display the price per unit for certain products. Shopify notes that displaying the price per unit is a legal requirement in some regions. ## How Uncap helps Uncap's guide to [why contractors stop ordering online](/post/contractor-supply-why-contractors-stop-ordering-online) names unit of measure as a reason trade accounts call the yard instead. Contractors do not order form ties in pieces; they order them in hundreds. They order dimensional lumber by the bundle, the unit or the linear foot. On top of Shopify B2B, the configuration work that turns a storefront into a contractor supply portal covers UOM mapping, job code fields and real-time inventory from the warehouse management system. ## Related terms - SKU (stock keeping unit) - Case pack - MOQ (minimum order quantity) - Item master - Catch weight - GTIN ## Sources - Microsoft Learn: Set up units of measure in Business Central - Shopify Help Center: Setting up quantity rules and volume pricing in B2B - Shopify Help Center: Displaying unit prices for products ## Frequently asked questions ### What does UOM mean on an invoice? UOM on an invoice means unit of measure: the unit each line quantity is counted in. A line of 10 with a UOM of case means 10 cases, not 10 pieces, so the buyer, seller and receiving dock all count the same thing. ### How is UOM calculated? A unit of measure conversion multiplies the quantity in the alternate unit by how many base units it contains. Five cases of 12 is 5 x 12 = 60 eaches. In Business Central, that per-unit quantity lives in the Qty. per Unit of Measure field. ### What is standard UOM? The standard, or base, unit of measure is the unit an item is stored in inventory. In Business Central the base unit of measure defines how the item is stored and is the basis for converting to alternate units such as cases or pallets. ### What is a UOM price? A UOM price is a price stated per unit of measure, such as per each, per case or per foot. A case of 12 at $30.00 is $2.50 per each. Shopify calculates a unit price from the price for the product's total units divided by the units it contains, then multiplied by the base measurement.