Convert between metric and imperial units for length, weight, temperature, volume, and speed. Select a category, choose your units, and get instant results.
The metric system (SI) is used by most countries worldwide and is based on powers of 10 — making conversions within the system straightforward (1 km = 1000 m, 1 kg = 1000 g).
The imperial system is primarily used in the United States, Liberia, and Myanmar. It uses less intuitive conversion factors (1 mile = 5,280 feet, 1 pound = 16 ounces) which is why a converter tool is helpful.
Celsius is based on the freezing (0°) and boiling (100°) points of water. Fahrenheit sets water's freezing at 32° and boiling at 212°. Kelvin starts at absolute zero (-273.15°C) and is used in scientific contexts — it has no negative values.
Conversions use standard conversion factors and are accurate to 6 decimal places. For most practical purposes (cooking, travel, fitness), this precision is more than sufficient.
Historical inertia. The US adopted the imperial system from Britain before the metric system was widely adopted. While science and medicine in the US use metric, everyday measurements (weather, road signs, recipes) remain imperial.
A US gallon is 3.785 liters while a UK (imperial) gallon is 4.546 liters. This converter uses US measurements. If you need UK conversions, multiply the US gallon result by 0.832.