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Unit Converter

Convert between all units instantly — length, weight, temperature, data, energy and more

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All Conversions

Categories

  • Length (20+ units)
  • Weight / Mass
  • Temperature
  • Area
  • Volume
  • Speed
  • Time
  • Digital Storage
  • Energy
  • Pressure
  • Angle
  • Frequency

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Free Unit Converter — All Categories

Convert between virtually any units across 13 categories including length, weight, temperature, area, volume, speed, time, digital storage, energy, pressure, angle, frequency and currency. Click any result in the "All Conversions" grid to instantly set it as your target unit.

Features

13 Categories

Length, weight, temperature, area, volume, speed, time, data, energy, pressure, angle, frequency and currency.

150+ Units

From nanometres to light-years, milligrams to tonnes — all common and scientific units included.

Swap Units

Instantly swap the from/to units with one click to reverse your conversion.

All Conversions Grid

See the value in every unit simultaneously — click any cell to select it as your target.

Temperature Special

Handles non-linear temperature conversions (°C, °F, K, Rankine, Delisle, Newton and more).

Currency Tab

Approximate exchange rates for 30+ currencies relative to USD.

Who Uses This Tool?

StudentsConvert between metric and imperial units for physics, chemistry and engineering.
TravellersConvert currencies, distances, temperatures and speeds when travelling internationally.
DevelopersConvert data storage units (bits, bytes, KB, MB, GB, TB) when working with file sizes.
CooksConvert cooking measurements between cups, tablespoons, millilitres and grams.

Frequently Asked Questions

Why does temperature conversion work differently?
Celsius, Fahrenheit and Kelvin have different zero points and scales, making them non-linear conversions. Our tool handles this correctly using the exact mathematical formulas for each conversion.
Are the currency rates live?
Currency rates are approximate reference values updated periodically. For financial transactions, always use a live currency exchange service.
What is the difference between a US and UK gallon?
A US gallon is 3.785 litres while a UK (Imperial) gallon is 4.546 litres — about 20% larger. Always specify which gallon when communicating volumes internationally.
What is a nautical mile?
A nautical mile (1,852 metres) is based on the circumference of the Earth and is used in navigation and aviation. It differs from a statute mile (1,609 metres) used in land travel.

Pro Tip

For the most accurate temperature conversions, remember: 0°C = 32°F = 273.15K. A quick mental trick: double the Celsius value and add 30 for a rough Fahrenheit estimate (e.g., 20°C ≈ 70°F).

Did You Know?

1875
Metric System Standardised
The International Metric System (SI) was formally established by the Treaty of the Metre in 1875, signed by 17 countries in Paris. Today, only the USA, Myanmar and Liberia officially use non-metric as their primary system.
299,792,458
Metres per Second
The speed of light in a vacuum is exactly 299,792,458 m/s. Since 1983, the metre is defined by this constant — making the speed of light the most precisely measured physical quantity.
1.8
Kg per Pound
One of the most commonly confused conversions: 1 pound = 0.4536 kg, so 1 kg ≈ 2.205 pounds. The confusion between pounds and kilograms has caused real disasters, including a 1999 NASA Mars orbiter crash costing $327 million.

Quick Conversion Cheatsheet

FromToMultiply By
MilesKilometres× 1.6093
PoundsKilograms× 0.4536
°Fahrenheit°Celsius(F − 32) × 5/9
Gallons (US)Litres× 3.7854
InchesCentimetres× 2.54
OuncesGrams× 28.3495
FeetMetres× 0.3048
AcresHectares× 0.4047

More Questions

What is the difference between mass and weight?
Mass (kilograms) measures the amount of matter in an object — it's the same everywhere in the universe. Weight (Newtons) measures the gravitational force on that mass — it changes on the Moon or in space. In everyday language we use "weight" to mean mass, but in science they are different. Our BMI and unit converters use mass.
Why does the US still use imperial units?
Congress actually authorized the metric system in 1866 and the US signed the Treaty of the Metre in 1875. Several attempts at metrication have failed due to economic costs of conversion, public resistance, and political opposition. The US military and science community use metric; consumer products largely use imperial.
What are the SI base units?
The International System (SI) has seven base units: metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). All other units (speed, force, energy, etc.) are derived from combinations of these seven.

Common Mistakes

Confusing US and UK gallons
A US gallon is 3.785 litres; a UK (Imperial) gallon is 4.546 litres — about 20% larger. Recipe disasters happen when cooks mix these up.
Always specify US or UK gallon when communicating volumes internationally.
Confusing weight and mass in nutrition
Nutritional labels show energy in kcal (Calories). 1 dietary Calorie = 1 kilocalorie = 4,184 joules. The lowercase "calorie" in chemistry is 1,000× smaller.
Dietary Calorie (Cal) = kilocalorie (kcal) — always check the context.
Assuming all cups are equal
A US cup is 236.6ml. A metric cup (AU, CA, NZ) is 250ml. A Japanese cup is 200ml. This 6% difference matters in baking.
Always check which cup measurement a recipe uses based on country of origin.