Free unit converter for length, weight, volume, area, and speed. Instantly convert between metric and imperial units with accurate, exact-factor results.
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Whether you're cooking with a recipe from another country, working on an international project, or solving homework problems, our unit converter handles all your conversion needs. Switch between metric and imperial units effortlessly with precise results.
Unit conversion is the process of changing a measurement from one unit to another while maintaining the same quantity. The world uses different measurement systems—metric (meters, kilograms, liters) predominates globally, while the US primarily uses imperial (feet, pounds, gallons). Understanding conversions is essential for international communication, science, cooking, travel, and countless everyday situations. The exact factors come from international standards — the SI (via the BIPM) defines the metric units, and the 1959 international yard-and-pound agreement fixes 1 inch = 2.54 cm and 1 pound = 0.45359237 kg exactly.
Conversion Principle
Convert cups to milliliters, ounces to grams, and tablespoons to teaspoons for international recipes.
Convert miles to kilometers, gallons to liters, and understand local measurement systems.
Switch between pounds and kilograms, miles and kilometers for workout logging.
Complete physics, chemistry, and engineering assignments requiring unit conversions.
Convert length, weight, volume, area, and speed in one convenient tool.
Get accurate conversions using exact conversion factors, not rounded approximations.
From everyday miles-to-kilometers to specialized units, we've got you covered.
The metric system was developed during the French Revolution for universal standardization. Most countries adopted it, but the US, Liberia, and Myanmar still primarily use imperial/customary units. This historical divide persists due to the cost and complexity of switching established systems.
Metric uses base-10 (meters, grams, liters) making mental math easier. Imperial uses varied bases (12 inches per foot, 16 ounces per pound) rooted in historical measurements. Metric is used in science worldwide, while imperial remains common in US daily life.
The most-used conversions: 1 mile = 1.609 km, 1 kg = 2.205 lb, 1 meter = 3.281 ft, 1 inch = 2.54 cm, 1 liter = 33.814 fl oz, and 1 acre = 4046.86 m². This tool covers length, weight, volume, area, and speed; for temperature, use our dedicated temperature converter.
Confusing fluid ounces (volume) with ounces (weight) is very common. A fluid ounce of water weighs about 1 ounce, but other substances differ. Also, UK and US gallons are different sizes—a UK gallon is about 20% larger than a US gallon.