You can turn unit of measure on and off in preferences.
With unit of measure turned on, you can show what quantities, prices, rates, and costs are based on. For example, if you provide a customer with consulting and you enter 4 on an invoice as the quantity for your Consulting service item, the unit of measure can show whether that quantity means four hours, four days, or four weeks. Or, if you enter a quantity of 25 on an invoice for the Ball Point Pen item, the unit of measure can show whether that quantity means 25 individual pens, 25 boxes of 12, or 25 cases containing 120 pens each.
QuickBooks provides two different ways or modes for assigning units of measure to items. You can choose to assign only one unit of measure to each item (Single U/M Per Item mode) or more than one unit of measure to each item (Multiple U/M Per Item mode).
In Single mode you can assign different units of measure to different items, but each item can have only one unit of measure assigned to it. You should choose Single mode only if you buy, stock, and sell each item by the same unit of measure. For example, choose this mode if you buy an item by the foot, keep track of it in inventory by the foot, and sell it by the foot.
You should choose Multiple mode if you buy, stock, or sell items in different units. For example, choose this mode if you buy an inventory item by the gallon and sell it by the ounce, or if you sell consulting services by both the hour and the day.
If you choose Multiple mode, you'll need to define unit of measure sets that you can assign to items. A unit of measure set consists of a base unit (usually the smallest unit used to track a certain type of item) and any number of related units (defined as containing a certain number of base units).
For example, you could create a unit of measure set called "Length by the inch" with a base unit of inch and related units of foot (containing 12 inches) and yard (containing 36 inches).
Another benefit of choosing Multiple mode is the ability to change or convert the unit of measure when you enter an item on a transaction form, such as an invoice or purchase order.
For example, suppose you have an item called Cable that you've assigned a unit of measure set that contains the inch, foot, and yard units of measure. If you enter Cable on an invoice with a quantity of 30 feet, you could then change the unit of measure to yards (causing 30 feet to become 30 yards) or convert the unit of measure to yards (causing 30 feet to become 10 yards).
Only certain versions of QuickBooks include unit of measure.