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Unit Converter

Convert length, mass, temperature, speed, volume and area using documented metric, international, UK imperial and US customary relationships.

Result
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Common Conversions

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About This Tool

What it does

Converts supported units through a documented SI base unit, while temperature uses the correct affine equations. UK imperial and US customary liquid units are labelled separately.

Who it's for

General-purpose conversion for everyday, educational and technical use. For regulated trade, laboratory or engineering work, retain the precision and standard required by the governing specification.

Your privacy

Values are converted locally in your browser. Binary floating-point can introduce tiny rounding differences, so results are displayed to up to 12 significant digits.

Constants and sources

Exact relationships are used where defined, including 1 inch = 0.0254 metre, 1 pound = 0.45359237 kilogram, 1 international nautical mile = 1,852 metres, 1 UK gallon = 4.54609 litres and 1 US gallon = 3.785411784 litres. Metric tablespoon and teaspoon are defined here as 15 mL and 5 mL. Sources reviewed 23 June 2026: BIPM SI Brochure; NIST SP 330; NIST SP 1038 conversion factors.

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Frequently Asked Questions

The tool covers length, mass, temperature, speed, volume and area. It labels UK imperial and US customary liquid units separately and includes metric tablespoon and teaspoon units.
Defined exact relationships are stored with their full stated values, such as 1 inch = 0.0254 m and 1 pound = 0.45359237 kg. Results are displayed with up to 12 significant digits because browser arithmetic uses binary floating point.
Yes. Zero and decimal values are accepted. Signed values are mathematically converted in every category. Temperature entries below absolute zero are rejected.
A UK imperial gallon is exactly 4.54609 litres. A US liquid gallon is exactly 3.785411784 litres, so the unit label matters.
Temperature is converted through Celsius using °C = (°F − 32) × 5/9 and K = °C + 273.15. Unlike scale-factor conversions, temperature requires both multiplication and an offset.
Swap reverses the From and To units and immediately recalculates the current value. Reset returns the current category to its first two units and clears the value and result.
Use it as a general converter. Regulated trade, laboratory and engineering work may require specified rounding, uncertainty, calibration or a jurisdiction-specific standard beyond this display.
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