# Conversion Calculator

> Convert between metric and imperial units of length, mass, area, volume, temperature, speed, pressure and energy with exact factors shown.

Category: Conversions & measurement · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/conversion-calculator

Pick a quantity, enter a value and choose the units to convert between. Every factor comes from the exact international definition of the unit, and the factor used is shown.

Also called: Unit converter, Metric conversion calculator.

## Inputs
- Quantity (options: Length, Weight / mass, Area, Volume, Temperature, Speed, Pressure, Energy; default length)
- Value (default 5)
- From (options: Millimetres (mm), Centimetres (cm), Metres (m), Kilometres (km), Inches (in), Feet (ft), Yards (yd), Miles (mi), Nautical miles (nmi); default mi)
- To (options: Millimetres (mm), Centimetres (cm), Metres (m), Kilometres (km), Inches (in), Feet (ft), Yards (yd), Miles (mi), Nautical miles (nmi); default km)
- From (options: Milligrams (mg), Grams (g), Kilograms (kg), Tonnes (t), Ounces (oz), Pounds (lb), Stones (st), US short tons, UK long tons; default lb)
- To (options: Milligrams (mg), Grams (g), Kilograms (kg), Tonnes (t), Ounces (oz), Pounds (lb), Stones (st), US short tons, UK long tons; default kg)
- From (options: Square millimetres (mm²), Square centimetres (cm²), Square metres (m²), Hectares (ha), Square kilometres (km²), Square inches (in²), Square feet (ft²), Square yards (yd²), Acres, Square miles (mi²); default ft2)
- To (options: Square millimetres (mm²), Square centimetres (cm²), Square metres (m²), Hectares (ha), Square kilometres (km²), Square inches (in²), Square feet (ft²), Square yards (yd²), Acres, Square miles (mi²); default m2)
- From (options: Millilitres (mL), Litres (L), Cubic metres (m³), US teaspoons, US tablespoons, US fluid ounces, US cups, US pints, US quarts, US gallons, Imperial fluid ounces, Imperial pints, Imperial gallons, Cubic inches (in³), Cubic feet (ft³); default gal_us)
- To (options: Millilitres (mL), Litres (L), Cubic metres (m³), US teaspoons, US tablespoons, US fluid ounces, US cups, US pints, US quarts, US gallons, Imperial fluid ounces, Imperial pints, Imperial gallons, Cubic inches (in³), Cubic feet (ft³); default l)
- From (options: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R); default c)
- To (options: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R); default f)
- From (options: Metres per second (m/s), Kilometres per hour (km/h), Miles per hour (mph), Knots (kn), Feet per second (ft/s); default kmh)
- To (options: Metres per second (m/s), Kilometres per hour (km/h), Miles per hour (mph), Knots (kn), Feet per second (ft/s); default mph)
- From (options: Pascals (Pa), Kilopascals (kPa), Bar, Standard atmospheres (atm), Pounds per square inch (psi), Millimetres of mercury (mmHg), Inches of mercury (inHg); default psi)
- To (options: Pascals (Pa), Kilopascals (kPa), Bar, Standard atmospheres (atm), Pounds per square inch (psi), Millimetres of mercury (mmHg), Inches of mercury (inHg); default bar)
- From (options: Joules (J), Kilojoules (kJ), Calories (cal), Kilocalories (kcal), Watt-hours (Wh), Kilowatt-hours (kWh), British thermal units (BTU); default kwh)
- To (options: Joules (J), Kilojoules (kJ), Calories (cal), Kilocalories (kcal), Watt-hours (Wh), Kilowatt-hours (kWh), British thermal units (BTU); default btu)

## Results
- Converted value
- Conversion used

## Formula

```
Result = Value × (size of the “from” unit ÷ size of the “to” unit). Temperatures also shift the zero point: °F = °C × 9/5 + 32, K = °C + 273.15.
```

Where:
- 1 in: 0.0254 m exactly
- 1 lb: 0.45359237 kg exactly
- 1 US gal: 3.785411784 L exactly
- 1 imperial gal: 4.54609 L exactly

## Worked example
1. 1 mile = 1,609.344 m by definition, and 1 km = 1,000 m.
2. So 1 mi = 1.609344 km.
3. 5 × 1.609344 = 8.04672 km.

**Result:** 5 miles is exactly 8.04672 kilometres.

## What the result means

Results are shown to 10 significant figures; round them to the precision of your original measurement.

## Assumptions and limits
- US customary cups, pints, quarts and gallons differ from imperial ones; both are listed separately.
- Calories are thermochemical (4.184 J); BTU is the International Table BTU (1,055.05585262 J).
- Currency is not converted, because exchange rates change constantly.
- Cooking conversions between volume and weight depend on the ingredient and are not included.

## Questions

### Why are there two kinds of gallon?

The US gallon is 3.785 L and the imperial (UK) gallon is 4.546 L, about 20% larger. Fluid ounces and pints differ too.

### What is the difference between a US ton and a tonne?

A tonne (metric ton) is 1,000 kg; a US (short) ton is 2,000 lb = 907.18 kg; a UK (long) ton is 2,240 lb = 1,016.05 kg.

## Sources
- [National Institute of Standards and Technology (NIST)](https://www.nist.gov/)

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/conversion-calculator