Unit Converter — Convert Any Measurement Instantly
Our free unit converter handles 15 categories of measurements with hundreds of units — from everyday conversions like feet to meters and Celsius to Fahrenheit, to specialized units like parsecs, pascals, and petabytes. Enter any value, select your units, and see instant conversions across the entire unit category at once.
Common Unit Conversions Reference
Length Conversions
| From | To | Multiply By |
|---|---|---|
| 1 inch | centimeters | 2.54 |
| 1 foot | meters | 0.3048 |
| 1 yard | meters | 0.9144 |
| 1 mile | kilometers | 1.60934 |
| 1 kilometer | miles | 0.621371 |
| 1 meter | feet | 3.28084 |
| 1 cm | inches | 0.393701 |
| 1 nautical mile | km | 1.852 |
Weight Conversions
| From | To | Multiply By |
|---|---|---|
| 1 kilogram | pounds | 2.20462 |
| 1 pound | kilograms | 0.453592 |
| 1 ounce | grams | 28.3495 |
| 1 gram | ounces | 0.035274 |
| 1 stone | kilograms | 6.35029 |
| 1 short ton | kilograms | 907.185 |
| 1 metric ton | pounds | 2,204.62 |
Temperature Conversions
| Conversion | Formula | Example |
|---|---|---|
| °C to °F | (°C × 9/5) + 32 | 100°C = 212°F |
| °F to °C | (°F - 32) × 5/9 | 32°F = 0°C |
| °C to K | °C + 273.15 | 0°C = 273.15K |
| K to °C | K - 273.15 | 373.15K = 100°C |
Volume Conversions
| From | To | Multiply By |
|---|---|---|
| 1 US gallon | liters | 3.78541 |
| 1 liter | US gallons | 0.264172 |
| 1 Imperial gal | liters | 4.54609 |
| 1 US cup | milliliters | 236.588 |
| 1 tablespoon | milliliters | 14.7868 |
| 1 teaspoon | milliliters | 4.92892 |
| 1 fluid ounce | milliliters | 29.5735 |
| 1 cubic foot | liters | 28.3168 |
Metric System Prefixes
The metric system uses standardized prefixes to represent multiples and fractions of base units. Understanding these prefixes unlocks all metric conversions:
| Prefix | Symbol | Factor | Example |
|---|---|---|---|
| Tera | T | 10¹² | 1 TB = 10¹² bytes |
| Giga | G | 10⁹ | 1 GHz = 10⁹ Hz |
| Mega | M | 10⁶ | 1 MW = 10⁶ watts |
| Kilo | k | 10³ | 1 km = 1,000 m |
| Hecto | h | 10² | 1 hm = 100 m |
| Deca | da | 10¹ | 1 dam = 10 m |
| Base | — | 10⁰ | meter, gram, liter |
| Deci | d | 10⁻¹ | 1 dm = 0.1 m |
| Centi | c | 10⁻² | 1 cm = 0.01 m |
| Milli | m | 10⁻³ | 1 mm = 0.001 m |
| Micro | μ | 10⁻⁶ | 1 μm = 10⁻⁶ m |
| Nano | n | 10⁻⁹ | 1 nm = 10⁻⁹ m |
| Pico | p | 10⁻¹² | 1 pm = 10⁻¹² m |
US vs Imperial (UK) Units — Key Differences
The United States and the United Kingdom both use "imperial" units but they are NOT identical. Several units have different values:
| Unit | US Value | UK (Imperial) Value | Difference |
|---|---|---|---|
| Fluid Ounce | 29.574 mL | 28.413 mL | US is 4% larger |
| Cup | 236.6 mL | 284.1 mL | UK is 20% larger |
| Pint | 473.2 mL | 568.3 mL | UK is 20% larger |
| Quart | 946.4 mL | 1,136.5 mL | UK is 20% larger |
| Gallon | 3,785.4 mL | 4,546.1 mL | UK is 20% larger |
| Ton (weight) | 907 kg | 1,016 kg | UK ton is larger |
Digital Storage: SI vs Binary
Digital storage has two competing conventions that use the same prefix names for different values:
| Unit | SI (Decimal) | Binary | IEC Name | Difference |
|---|---|---|---|---|
| Kilobyte (KB) | 1,000 bytes | 1,024 bytes | KiB | 2.4% |
| Megabyte (MB) | 1,000,000 B | 1,048,576 B | MiB | 4.9% |
| Gigabyte (GB) | 10⁹ bytes | 2³⁰ bytes | GiB | 7.4% |
| Terabyte (TB) | 10¹² bytes | 2⁴⁰ bytes | TiB | 10% |
| Petabyte (PB) | 10¹⁵ bytes | 2⁵⁰ bytes | PiB | 12.6% |
Speed Conversions
| From | mph | km/h | m/s | knots |
|---|---|---|---|---|
| 1 mph | 1 | 1.609 | 0.447 | 0.869 |
| 1 km/h | 0.621 | 1 | 0.278 | 0.540 |
| 1 m/s | 2.237 | 3.600 | 1 | 1.944 |
| 1 knot | 1.151 | 1.852 | 0.514 | 1 |
| Mach 1 | 767 | 1,235 | 343 | 667 |
Frequently Asked Questions
How many cm are in an inch?
There are exactly 2.54 centimeters in one inch. This is the defined conversion factor — 1 inch = 2.54 cm exactly. To convert any number of inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54.
How many feet are in a meter?
One meter equals approximately 3.28084 feet. More precisely, 1 meter = 100/30.48 feet (since 1 foot = 30.48 cm exactly). To convert meters to feet, multiply by 3.28084. To convert feet to meters, multiply by 0.3048.
What is 1 stone in kg?
One stone equals 14 pounds, which equals approximately 6.35029 kilograms. The stone is still commonly used for body weight in the UK and Ireland. To convert stone to kg, multiply by 6.35029. A person weighing 11 stone weighs 69.85 kg or about 154 lbs.
How do you convert knots to mph?
Multiply knots by 1.15078 to get mph. One knot equals exactly one nautical mile per hour. One nautical mile is 1,852 meters, which is approximately 1.15078 statute miles. So 20 knots = 23.02 mph = 37.04 km/h.
What is the difference between mass and weight?
Mass is the amount of matter in an object and does not change regardless of location (measured in kg). Weight is the gravitational force acting on that mass and varies by location (measured in Newtons). On Earth's surface, 1 kg of mass has a weight of approximately 9.81 Newtons. In everyday use, weight and mass are used interchangeably, though scientifically they differ.