Unit Converter
Convert between metric and imperial units — length, weight, temperature, and volume.
What this calculator does
Converts a value between units within the same category — length, weight, volume, or temperature — so you can move between metric and US customary measurements without doing the arithmetic by hand. Enter an amount, pick your source and target unit, and it returns the converted figure instantly.
Who this is for
Anyone working across measurement systems: cooks following a recipe written in the "wrong" units for their kitchen scales, students and professionals converting between metric and imperial for coursework or specs, travelers making sense of foreign temperature forecasts or road-sign distances, and anyone double-checking a package or shipping weight given in an unfamiliar unit.
How this calculator works
Length, weight, and volume conversions go through a common base unit (meters, kilograms, liters). Temperature uses direct formulas since Celsius/Fahrenheit/Kelvin scales don't share a simple multiplier.
The formula
For length, weight, and volume, every unit has a fixed conversion factor to its category's base unit — for example, 1 mile = 1,609.34 meters, 1 pound = 0.453592 kilograms. To convert between any two units in the same category, the calculator converts your input to the base unit first, then converts that base value to your target unit. For temperature, the formulas are fixed and non-linear: Celsius to Fahrenheit is °F = (°C × 9/5) + 32, and Fahrenheit to Celsius is °C = (°F − 32) × 5/9. Kelvin is simply Celsius + 273.15, with no multiplier involved.
Worked example
Converting 5 miles to kilometers: 5 × 1.60934 = 8.05 km. Converting 98.6°F (a common "normal body temperature" reference) to Celsius: (98.6 − 32) × 5/9 = 66.6 × 5/9 = 37°C, which is why 37°C is the commonly cited average body temperature in Celsius.
Your amount across common units
Run the calculator above to see your amount converted across several common units in the same category.
Common mistakes
- Mixing up mass and weight. Kilograms measure mass, not weight (force) — for everyday conversions this distinction rarely matters, but it's worth knowing the difference is real in physics.
- Rounding too early. For precise applications (cooking, engineering, medication dosing), use the full decimal result rather than a rounded intermediate figure.
- Confusing US and UK volume units. A US gallon and UK (imperial) gallon are different sizes — this calculator uses US customary units, so double-check if you need imperial UK measures.
- Applying a length/weight-style multiplier to temperature. Temperature scales don't share a common zero point, so you can't scale a Celsius reading by a fixed factor to get Fahrenheit — the formula requires both a multiplication and an addition step.
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Frequently Asked Questions
Are these US or UK/imperial units?
Volume conversions use US customary units (US gallon, US cup, etc.), which differ from UK imperial measures. Length and weight units are the same across US and UK systems.
How accurate are these conversions?
They use standard, widely accepted conversion factors and should be accurate for everyday use. For scientific or engineering applications requiring extreme precision, verify against an authoritative reference.
Why does temperature work differently from other units?
Celsius, Fahrenheit, and Kelvin don't share a common zero point or simple multiplier the way length or weight units do, so temperature conversion uses direct formulas rather than a shared base unit.
Why is a US gallon different from a UK gallon?
The two countries standardized volume measures separately — a US gallon is about 3.785 liters, while a UK (imperial) gallon is about 4.546 liters, roughly 20% larger. Always check which system a recipe or spec is using before converting.
What's the base unit used for length conversions?
Meters. Every length unit — miles, feet, inches, yards, kilometers — is converted to meters first, then from meters to your target unit, which keeps the conversion factors consistent and accurate across any pair of units.