Unit Converter

This free unit converter instantly converts length, weight, area, volume and temperature units — inch to cm, mile to km, gallon to litre, Fahrenheit to Celsius and 50+ more. One tool for every unit conversion you need, it also works as a cubic meter calculator, an m3 calculator and a liter calculator, with accurate results for both everyday use and technical work.

What Is a Unit Converter?

This unit converter lets you instantly perform any unit conversion across length, weight, area, volume and temperature. It covers the most-asked conversions like inch-cm, mile-km, gallon-litre and Fahrenheit-Celsius, plus many more such as meter-foot, yard-meter and cubic meter-litre. It gives fast, accurate results for both everyday use and technical calculations.

Units of Length — How Many CM in an Inch, How Many KM in a Mile

Conversions between the units of length are among the most common unit questions. The metre is the SI base unit, and all other length units relate back to it. The most frequent length conversions:

The basic rule for converting between length units: first convert everything to meters, then to the target unit. This tool does that automatically.

Volume Units — How Many Litres in a Gallon, mL in a Litre, Cubic Meters

The most-asked volume questions are gallon-litre and litre-millilitre conversions:

• How many litres in a gallon: 1 US gallon = 3.78541 litres. For example, 10 gallons = 37.85 litres.
• UK gallon: 1 imperial gallon = 4.54609 litres (different from the US gallon).
• How many mL in a litre: 1 litre = 1,000 millilitres.
• How many litres in a cubic meter: 1 m³ = 1,000 litres.
• Volume to litres: Volume (m³) × 1,000 = litres.
• How many litres in 1 kg: for pure water, 1 kg = 1 litre; it varies with density (e.g. oil ≈ 0.92 L/kg).

The cubic-meter formula is: Length (m) × Width (m) × Height (m). For example, 2 m × 3 m × 1.5 m = 9 m³. To convert the result to litres, multiply by 1,000 (9 m³ = 9,000 litres). As a cubic meter calculator (or m3 calculator) and a liter calculator, this tool handles both the volume formula and the litre conversion in one step.

Temperature Units — Fahrenheit, Celsius, Kelvin

Fahrenheit is used in the US and a few other countries, while Celsius is preferred worldwide. The SI unit of temperature is the Kelvin (K); everyday life uses Celsius (°C) or Fahrenheit (°F).

• Fahrenheit to Celsius: °C = (°F − 32) × 5/9  |  Example: 98.6°F = 37°C
• Celsius → Fahrenheit: °F = °C × 9/5 + 32  |  Example: 100°C = 212°F
• Celsius → Kelvin: K = °C + 273.15  |  Example: 0°C = 273.15 K
• 1 Fahrenheit in Celsius: 0°F = −17.78°C
• 1 Celsius in Fahrenheit: 33.8°F
• 1 Kelvin in Celsius: −272.15°C

What measures temperature: a thermometer; the SI unit is the Kelvin. In everyday use, Celsius or Fahrenheit thermometers are used.

Weight Units — Kilogram, Pound, Ounce, Gram Conversions

Converting between weight units is often needed in international shopping, recipes and fitness tracking. The most common weight units are the kilogram (kg), pound (lb) and ounce (oz).

• 1 pound in grams: 1 lb = 453.592 grams.
• 1 pound in kg: 1 lb ≈ 0.4536 kg.
• 1 kg in pounds: 1 kg ≈ 2.2046 lb.
• 1 ounce (oz) in grams: 1 oz = 28.3495 grams.
• 1 kg in ounces: 1 kg ≈ 35.274 oz.
• 1 tonne in kg: 1 metric tonne = 1,000 kg.

Use this unit converter for portion weights in diet and nutrition tracking, package weights in e-commerce and shipping, or kilogram-pound conversions from international recipes.

Area Units — m², Hectare, Acre, Square Foot Conversions

Area measurement is critical in real estate, agriculture and construction. Square meter (m²), hectare (ha), acre and square foot (ft²) are the most common area units worldwide.

• 1 hectare in m²: 1 hectare = 10,000 m².
• 1 acre in m²: 1 acre ≈ 4,046.86 m².
• 1 acre in hectares: 1 acre ≈ 0.4047 hectares.
• 1 km² in m²: 1 km² = 1,000,000 m².
• 1 square foot (ft²) in m²: 1 ft² ≈ 0.0929 m².
• 1 square mile in km²: 1 mi² ≈ 2.59 km²; common in US-sourced geographic comparisons.

To convert land sizes given in acres, hectares or square meters between each other, use the "Area" tab above.

Length Measurement and Unit Systems — SI vs. Imperial

Length measurement happens in two different systems. Most of the world uses the SI (International System of Units): meter, kilometer, centimeter and millimeter belong to it. The US, the UK and a few countries still use the Imperial System: inch, foot, yard and mile.

1 centimeter in millimeters: 1 cm = 10 mm. 1 millimeter in meters: 1 mm = 0.001 m. The base reference for converting between length units is the meter; all other length units are defined relative to it. Understanding the relationship between length units is useful in everything from daily life to engineering.

How to Use This Unit Converter

Choose the category you want from the tabs at the top: Length, Weight, Area, Volume or Temperature. Pick your units from the "From Unit" and "To Unit" dropdowns, enter the value and the result is calculated instantly. Use the "Popular" shortcut buttons to convert inches to cm, miles to km, pound-kg, Fahrenheit-Celsius and gallon-litre with one click. You can copy the result to your clipboard. See the FAQ for more. This unit converter handles conversions between different unit systems quickly and accurately, with all categories on a single screen.