Are the conversion factors exact?

Yes. Every factor is an internationally defined constant — one inch is exactly 25.4 mm, one pound is exactly 0.45359237 kg, one US gallon is exactly 3.785411784 L. The page lists the exact constant behind each unit so you can verify the maths.

Why are there separate US and UK pints and gallons?

Because they are genuinely different units. A US pint is about 473 ml while a UK pint is about 568 ml; a US gallon is about 3.785 L while a UK gallon is about 4.546 L. Both are listed separately so you convert the right one.

How is temperature converted?

With offset formulas, not a factor, because the scales have different zero points: °C to °F is × 9/5 + 32, °C to K is + 273.15. The tool applies the correct formula for the direction you choose.

Why does the result show scientific notation?

For very large or very small values the tool switches to scientific notation to stay readable. Everyday values are shown in normal notation with locale-correct decimal separators and trailing zeros trimmed.

Does it convert speed, area or data units?

Not yet — the converter covers length, volume, weight and temperature, the four categories most expats and travellers need. Additional categories can be added as the site grows.

Convert

Convert between metric and imperial units for length, volume, weight and temperature. Pick a category, choose your units, and enter a value.

Unit conversion is the quiet everyday problem of living between systems — a recipe in cups, a road sign in kilometres, a weather forecast in Fahrenheit. A single converter that handles length, volume, weight and temperature removes the mental arithmetic.

When to use this

Use the unit converter whenever a number arrives in a system you do not use: cooking from a foreign recipe, reading a distance on a road sign, weighing luggage against an airline limit quoted in kilograms, or making sense of a weather forecast in Fahrenheit. Swapping units instantly shows the same quantity in the system you know.

It is a measurement tool, not a currency or translation tool — for money use the Currency converter, for foreign words use Translate. The converter assumes you already know which unit the original number is in; if you are unsure, the unit labels in the dropdowns spell out each one in full.

How this works

Every unit in a category is stored with its exact conversion factor to the category's base unit — the metre for length, the litre for volume, the kilogram for weight. To convert, the tool first turns your input into the base unit by multiplying by the source unit's factor, then turns that base value into the target unit by dividing by the target unit's factor. The factors are exact, internationally defined constants, not rounded approximations: one inch is exactly 25.4 millimetres, one pound is exactly 0.45359237 kilograms, one US gallon is exactly 3.785411784 litres.

Temperature cannot use a simple factor because the Celsius, Fahrenheit and Kelvin scales have different zero points. The tool handles it with the standard offset formulas: Celsius to Fahrenheit is × 9/5 + 32, Celsius to Kelvin is + 273.15, with the reverse operations for the other direction. The page lists the exact constant behind every unit so the maths is verifiable.

Results are formatted with locale-aware decimal separators and trimmed of trailing zeros, with scientific notation for very large or very small values. The converter assumes you entered a valid number and a sensible unit pair; it does not account for the difference between US and UK volume units (both are listed separately), or for the historical regional variations of units that are now standardised internationally.

Worked example

A US recipe calls for 2 cups of flour, but your kitchen scale and measuring jug are metric.

1Choose the Volume category, set the source unit to Cup (US) and the target to Millilitre (ml).
2Enter 2 in the amount field.
3The tool converts via the litre: 2 × 0.2365882365 = 0.473176473 L, then ÷ 0.001 = 473.18 ml.
4Switch the target to Fluid ounce (US) to see the same amount as about 16 fl oz — the recipe's original measure.

Frequently asked questions

Are the conversion factors exact?: Yes. Every factor is an internationally defined constant — one inch is exactly 25.4 mm, one pound is exactly 0.45359237 kg, one US gallon is exactly 3.785411784 L. The page lists the exact constant behind each unit so you can verify the maths.
Why are there separate US and UK pints and gallons?: Because they are genuinely different units. A US pint is about 473 ml while a UK pint is about 568 ml; a US gallon is about 3.785 L while a UK gallon is about 4.546 L. Both are listed separately so you convert the right one.
How is temperature converted?: With offset formulas, not a factor, because the scales have different zero points: °C to °F is × 9/5 + 32, °C to K is + 273.15. The tool applies the correct formula for the direction you choose.
Why does the result show scientific notation?: For very large or very small values the tool switches to scientific notation to stay readable. Everyday values are shown in normal notation with locale-correct decimal separators and trailing zeros trimmed.
Does it convert speed, area or data units?: Not yet — the converter covers length, volume, weight and temperature, the four categories most expats and travellers need. Additional categories can be added as the site grows.

Related tools

Conversion factors are internationally defined constants (SI definitions, the international yard and pound agreements, and US/UK customary unit definitions). No external data source. Last updated: September 2026.

These tools are provided for general everyday use. Translation, definitions and synonyms are machine- or community-generated and may contain errors; exchange rates are reference values and not transaction rates; unit conversions use exact constants but do not account for regional unit variants beyond those listed. Always confirm critical information with an authoritative source before acting on it.