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Unit converter

Easily convert between units of length, weight, temperature, area and volume, and see a table of every conversion.

Required fields are marked with an asterisk (*).

The number you want to convert.
Choose the category of units to convert between.
The unit you start from.
The target unit to convert to.

This converter transforms values between units of the same category: length, weight, temperature, area or volume. Conversions are precise using fixed factors, except temperature which uses a special affine relationship (Celsius ↔ Fahrenheit ↔ Kelvin).

Formula

Conversion = value × source-unit factor ÷ target-unit factor (temperature uses a special affine offset).

When is this useful?

Use it for cooking recipes (ml/l), buying land or construction (m²/acre), sport and dieting (kg/lb), or converting temperatures between scales.

Worked example

Example using the calculator’s values: 1000 from m to km.
The result is 1 km, and the table shows 1000 m = 1,000,000 mm.

Assumptions

  • Both units must belong to the same category (you cannot convert kilograms to litres).
  • Conversion factors are precise to SI factors or established imperial ones.
  • The US gallon is used (not the imperial gallon).
  • The all-conversions table shows the value in every unit of the chosen category.

Common mistakes

  • Confusing the US gallon with the imperial gallon — the calculator uses the US gallon.
  • Trying to convert units from different categories (such as pounds to litres).
  • Forgetting that Celsius and Kelvin start from different zero points, so the relationship is not a constant factor.
  • Picking the same unit for both sides — the calculator blocks it with an error.

Frequently asked questions

Why can’t I convert pounds to litres?

Pounds measure weight and litres measure volume — they are different categories. Conversion is only possible between units of the same category.

Is the stone unit imperial?

Yes. The stone is a British weight unit equal to 14 pounds (6.35 kg), still common in the UK.

Why does temperature use addition and subtraction rather than only multiplication?

Because Kelvin starts at absolute zero while Celsius and Fahrenheit have a different zero point, so the relationship is affine rather than a constant ratio.

Methodology and review

The calculator uses fixed conversion factors from the International System of Units applied around a base unit (metre/kilogram/litre), and handles temperature with a special affine relationship. Results are rounded for display and may carry tiny differences.

Standard ratios are as adopted globally; some local units (such as acre-equivalents) differ between countries.

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