Unit Converter
Convert between common metric, imperial and scientific units. Choose a category, enter a value, select the “from” and “to” units, then view the result, worked steps and the same value converted into every available unit in that category.
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Common conversions in this category
How the converter works
For most categories, the converter uses a single base unit. For example, length values convert through metres, mass values convert through kilograms, speed values convert through metres per second, and energy values convert through joules. Your input is first converted into the base unit, then converted into the target unit.
This approach avoids inconsistent chained conversions. Temperature is handled separately because temperature scales use offsets as well as scaling. For example, converting Celsius to Fahrenheit requires multiplying by 9/5 and then adding 32.
Practical real-life uses
Travel and driving
Convert miles to kilometres, mph to km/h, or fuel-related measurements before estimating a journey.
Home and bills
Convert watts, kilowatts, joules and kWh when checking appliance running costs.
DIY and shopping
Convert inches to centimetres, metres to feet, litres to pints, or square metres to square feet.
Study and engineering
Convert pressure, energy, power and time units while keeping the calculation consistent.
Common conversion mistakes
- •Mixing metric and imperial: convert everything into one unit system before using a formula.
- •Using the wrong gallon: UK gallons and US gallons are different, which affects fuel and volume calculations.
- •Confusing power and energy: kW is power; kWh is energy. A 2 kW heater running for 3 hours uses 6 kWh.
- •Rounding too early: keep extra precision during intermediate steps and round at the end.
Sources and assumptions
This converter is intended for general calculation, education and everyday planning. Conversion factors are based on widely used SI definitions and common exact relationships where applicable. Results are rounded according to the decimal-place setting selected by the user.
- Exact definitions: examples include 1 inch = 2.54 centimetres, 1 foot = 0.3048 metres, 1 mile = 1,609.344 metres and 1 pound = 0.45359237 kilograms.
- Temperature conversions: Celsius, Fahrenheit and Kelvin use formulas with offsets, so they are not handled as simple ratio conversions.
- Energy and power: joules, watt-hours and kilowatt-hours are treated using standard relationships, including 1 Wh = 3,600 J and 1 kWh = 3,600,000 J.
- Pressure conversions: pressure values use common engineering conversion factors. For safety-critical pressure work, always confirm values against equipment documentation and official standards.
- Rounding: displayed results are rounded for readability. Use more decimal places where precision matters.
- Limitations: this page is not a substitute for calibrated measuring equipment, engineering standards, medical guidance, legal metrology or safety-critical documentation.