What Are US Customary Units?
US customary units are the system of measurement commonly used in the United States, including inches, feet, miles, ounces, pounds, fluid ounces, cups, and gallons. They are defined in terms of metric units; for example, one inch is exactly 2.54 cm and one pound is exactly 0.45359237 kg.
US vs. Imperial
The British imperial system shares many unit names, but some volumes differ: a US gallon is about 3.785 liters, while an imperial gallon is about 4.546 liters.
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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.