What is unit conversion?
Unit conversion is the process of expressing a measurement in a different unit without changing the underlying physical quantity.
For example, a distance of one metre can also be expressed as approximately 3.28084 feet. The numerical value changes, but the physical length remains the same.
This conversion calculator supports four measurement categories: length, mass, volume and temperature.
Metres, kilometres, centimetres, inches, feet and miles.
Kilograms, grams, pounds and ounces.
Litres, millilitres, US gallons and Imperial gallons.
Celsius, Fahrenheit and Kelvin.
How to use the conversion calculator
- Enter the value. Type the number you want to convert.
- Choose the quantity. Select Length, Mass, Volume or Temperature.
- Select the source unit. Choose the unit your original measurement uses.
- Select the target unit. Choose a compatible unit for the result.
- Calculate. Select Calculate to view the converted value.
Unit conversion formulas
Most length, mass and volume conversions use a multiplication or division factor. Temperature conversion requires an additional offset in some cases.
Converted value = Original value × Source unit factor ÷ Target unit factor
The source and target factors must refer to the same reference unit.
Metres to feet formula
Feet = Metres × 3.280839895
Kilograms to pounds formula
Pounds = Kilograms × 2.2046226218
Litres to US gallons formula
US gallons = Litres ÷ 3.785411784
Celsius to Fahrenheit formula
Fahrenheit = Celsius × 9 ÷ 5 + 32
Fahrenheit to Celsius formula
Celsius = (Fahrenheit − 32) × 5 ÷ 9
Celsius to Kelvin formula
Kelvin = Celsius + 273.15
Worked conversion examples
Example 1: Convert 1 metre to feet
- Value: 1
- Quantity: Length
- From: m
- To: ft
1 × 3.280839895 = 3.280839895 feet.
Result: approximately 3.28084 ft.
Example 2: Convert 10 kilograms to pounds
- Value: 10
- Quantity: Mass
- From: kg
- To: lb
10 × 2.2046226218 = 22.046226218 pounds.
Result: approximately 22.0462 lb.
Example 3: Convert 5 litres to US gallons
- Value: 5
- Quantity: Volume
- From: L
- To: US gallon
5 ÷ 3.785411784 ≈ 1.32086 US gallons.
Result: approximately 1.32086 US gal.
Example 4: Convert 25°C to Fahrenheit
- Value: 25
- Quantity: Temperature
- From: Celsius
- To: Fahrenheit
25 × 9 ÷ 5 + 32 = 77.
Result: 77°F.
Common length conversions
These reference values use standard metric and international unit definitions.
| Unit | Equivalent |
|---|---|
| 1 metre | 100 centimetres |
| 1 kilometre | 1000 metres |
| 1 inch | 2.54 centimetres |
| 1 foot | 0.3048 metres |
| 1 mile | 1.609344 kilometres |
| 1 metre | 3.280839895 feet |
Mass and weight conversions
In everyday usage, weight is often expressed in kilograms or pounds, although these are technically units of mass rather than force.
| Unit | Equivalent |
|---|---|
| 1 kilogram | 1000 grams |
| 1 pound | 0.45359237 kilograms |
| 1 ounce | 28.349523125 grams |
| 1 kilogram | 2.2046226218 pounds (approx.) |
Volume conversions: litres and gallons
Volume conversions are particularly important when working with US and UK measurement systems. The US liquid gallon and Imperial gallon represent different volumes.
| Unit | Equivalent |
|---|---|
| 1 litre | 1000 millilitres |
| 1 US liquid gallon | 3.785411784 litres |
| 1 Imperial gallon | 4.54609 litres |
| 1 US liquid gallon | 0.832674 Imperial gallons (approx.) |
Celsius, Fahrenheit and Kelvin conversion
Unlike length and mass conversions, temperature scales have different zero points. Therefore, multiplying by a conversion factor alone is not always sufficient.
| Temperature | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Water freezing point* | 0°C | 32°F | 273.15 K |
| Room temperature example | 20°C | 68°F | 293.15 K |
| Warm day example | 30°C | 86°F | 303.15 K |
| Water boiling point* | 100°C | 212°F | 373.15 K |
*The water freezing and boiling examples are conventional approximate reference points at standard atmospheric pressure; actual phase-change temperatures depend on conditions.
Metric vs Imperial vs US customary units
The metric system uses decimal-based units such as metres, kilograms and litres. The Imperial and US customary systems use units including inches, feet, miles, pounds and gallons.
Some units have the same names but different definitions across systems. For example, the Imperial gallon is larger than the US liquid gallon.
When converting recipes, fuel volumes or technical measurements, check which system the original measurement uses.
Conversion accuracy and rounding
Many unit conversion factors are defined exactly, while the displayed result may be rounded for readability.
For example, one metre equals approximately 3.280839895 feet. Displaying 3.28 feet is easier to read, but less precise.
For practical calculations, retain sufficient decimal places until the final result. For engineering or scientific work, use precision appropriate to the original measurement and its uncertainty.
Common unit conversion mistakes
- Mixing units from different physical quantities.
- Confusing US gallons with Imperial gallons.
- Treating Celsius and Fahrenheit as simple multiplication-only conversions.
- Rounding intermediate values too early.
- Confusing mass units with units of force.
- Selecting the wrong source or target unit.
Limitations of this conversion calculator
The tool supports the units available in its four measurement categories. It is not intended to convert unrelated quantities, currencies or specialised engineering units that are not listed.
Results depend on the selected units, conversion factors and numerical precision used by the calculator implementation.
Frequently asked questions
How do I convert metres to feet?
Multiply the value in metres by approximately 3.280839895. For example, 2 metres is approximately 6.56168 feet.
How many centimetres are in one inch?
One international inch is exactly 2.54 centimetres.
How do I convert kilograms to pounds?
Multiply kilograms by approximately 2.2046226218. For example, 10 kg is approximately 22.0462 lb.
Are US and Imperial gallons the same?
No. One US liquid gallon equals 3.785411784 litres, while one Imperial gallon equals 4.54609 litres.
How do I convert Celsius to Fahrenheit?
Multiply Celsius by 9/5 and add 32. For example, 25°C equals 77°F.
Can I convert negative temperatures?
Negative Celsius and Fahrenheit temperatures are valid inputs. Kelvin values cannot be below absolute zero.
Can I convert between different quantities?
No. The source and target units must represent the same quantity, such as length to length or mass to mass.
Does the calculator work on mobile devices?
The page uses responsive layouts intended for mobile phones, tablets and desktop browsers.
Are my conversion values uploaded?
The calculator is designed to perform calculations in your browser. Website analytics and advertising may operate separately.
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