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Unit Converter

Convert between units of length, weight, volume, speed, area and more. Fast and accurate unit conversion for everyday tasks, cooking, science and engineering.

Last reviewed 15 August 2026Reviewed after a methodology change

Your details

Calculator inputs
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When to use this calculator

  • When you need a fast estimate before making a bigger decision.
  • When you want to compare a few scenarios using the same assumptions.
  • When you need a clearer starting point before using a detailed quote or formal document.
  • When you want to sanity-check a figure you have seen elsewhere.

A realistic planning example

Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.

A realistic planning example
InputValue
Value100
Conversion Factor (multiply by)0.621371

After entering these figures, focus on result first and then rerun the tool with a more cautious assumption.

How to read your results

Result

The figure produced by this output for the inputs you entered. Change one variable at a time if you want to see what drives it.

Method & assumptionsAuthoritative sources

This converter uses internationally recognised conversion factors as defined by the International Bureau of Weights and Measures (BIPM) and, where applicable, UK statutory instruments. Conversions between metric and imperial units are exact where the definition is exact (such as the inch-to-millimetre relationship) and carry only the precision of the underlying constant where approximate. The tool covers common categories including length, mass, volume, temperature, area, and speed. Temperature conversions between Celsius, Fahrenheit, and Kelvin use the standard offset formulae. Note that the tool converts units of measurement only — it does not handle currency, data storage sizes, or cooking volume equivalents such as cups and tablespoons, which use variable definitions depending on country.

Common mistakes

  • !Using an assumption that is not supported by a current local quote, bill, statement or official source.
  • !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
  • !Mixing monthly and annual inputs without converting them consistently.
  • !Testing only one scenario instead of checking how a cautious assumption changes the result.

What to do next

  • Run a second scenario with a cautious assumption so you can see the downside clearly.
  • Compare the result with the related calculators below before making a decision.
  • Check current local rules, eligibility and provider terms before applying or committing money.
  • Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.

Keep exploring

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Frequently asked

The UK officially uses metric for trade and regulation (kg, km, litre, Celsius), but imperial units remain in common use for road distances (miles), beer and milk (pints), draught cider, and body weight (stones and pounds). Since 2023 traders can display either system as primary, provided the other is shown alongside.

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