US customary and metric converter
Unit converter for the US
Convert the measurements US users see every day: customary units for construction, vehicles, recipes, weather, land and shipping, plus metric units used in science, medicine, product specs, imports and international work.
- Convert inches, feet, miles, pounds, ounces, gallons, cups and Fahrenheit alongside cm, meters, kg, liters and Celsius.
- Built for US contexts such as DIY, healthcare, e-commerce, automotive parts, recipes, land, travel and packaging.
- Plain-English guidance on when a quick rounded result is enough and when technical precision matters.
Unit converter
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Weight and mass
Temperature
Volume
Speed
Area
Power
Angle
How to convert units in the US
The United States mixes US customary units with the metric system more than most people realize. Daily life still uses inches, feet, miles, pounds, gallons and Fahrenheit, while medicine, science, global manufacturing, product imports and many technical specifications use SI or metric units.
Why US users need both systems
NIST describes the International System of Units as the international standard for measurement and provides official US representation in international standards work. At the same time, US customary units remain common in consumer life, construction, vehicles, road distances, food packaging and weather.
That makes a US converter different from a pure metric calculator. It needs to move comfortably between inches and centimeters, pounds and kilograms, Fahrenheit and Celsius, gallons and liters, and square feet and square meters.
Common US conversions
- Inches, feet and yards to centimeters or meters for furniture, screens, parts, DIY and building materials.
- Pounds and ounces to kilograms and grams for shipping, fitness, medical records, food and product specs.
- Fahrenheit to Celsius for travel, science, medical devices, recipes and international weather.
- Gallons, quarts, cups and fluid ounces to liters or milliliters for fuel, recipes, cleaning supplies and lab-style measures.
- Miles and mph to kilometers and km/h for travel, imported vehicles and international instructions.
- Square feet and acres to square meters or hectares for property, land, flooring, paint and landscaping.
When rounding is safe
For shopping, travel and rough comparisons, one or two decimal places is usually enough. For medication, engineering, machining, load ratings, construction tolerances, lab work or product labels, preserve more precision and verify the required tolerance before ordering, cutting, dosing or publishing a value.
Which category to choose
Use length for inches, feet, yards, miles, centimeters, meters and kilometers. Use weight and mass for ounces, pounds, grams and kilograms. Use temperature for Fahrenheit and Celsius. Use volume for teaspoons, cups, fluid ounces, gallons, milliliters and liters. Use area for square feet, acres, square meters and hectares.
Preguntas frecuentes
Does the US use metric or customary units?
Both. US customary units are common in daily life, while metric and SI units are common in science, medicine, international trade, product specs and many technical settings.
What are the most useful US conversions?
Inches to centimeters, pounds to kilograms, Fahrenheit to Celsius, gallons to liters, miles to kilometers and square feet to square meters are among the most common.
When should I keep more decimal places?
Keep more precision for medicine, engineering, machining, construction, lab work, load ratings and product labeling. Rounded values are fine for quick everyday comparisons.
Why does a US converter include metric units?
Metric units appear in imported products, science classes, healthcare records, nutrition labels, international shipping, automotive specs and technical documentation.
