Unit Conversion Calculator
Select a category, enter your value, and convert any unit instantly.
What Is a Unit Conversion Calculator?
A unit conversion calculator is an online tool that instantly converts a measurement from one unit to another within the same category — such as meters to feet, Celsius to Fahrenheit, or kilograms to pounds. Our free converter supports six major measurement systems: Length, Mass, Temperature, Volume, Area, and Time — covering both the metric (SI) system and the imperial system used in the U.S. and UK.
Unit Conversion Categories — What You Can Convert
1. Length Conversion (Meters, Feet, Miles & More)
Convert between kilometers to miles, meters to feet, centimeters to inches, yards to meters, and more. Length unit conversion is critical for construction, travel, navigation, sports, and scientific research. Common conversions: 1 mile = 1.60934 km, 1 foot = 0.3048 meters, 1 inch = 2.54 cm.
2. Mass Conversion (kg to lbs, Grams to Ounces & More)
Easily convert kilograms to pounds, grams to ounces, milligrams to grams, and more. Weight and mass conversion is widely used in cooking, fitness, medicine, and shipping. Common conversions: 1 kg = 2.20462 lbs, 1 pound = 453.59 grams, 1 ounce = 28.35 grams.
3. Temperature Conversion (Celsius, Fahrenheit & Kelvin)
Convert Celsius to Fahrenheit, Fahrenheit to Celsius, and both to Kelvin for scientific use. Temperature conversion is essential for weather interpretation, cooking, lab work, and international travel. Key formulas: °F = (°C × 1.8) + 32; K = °C + 273.15.
4. Volume Conversion (Liters, Gallons, mL & More)
Convert liters to gallons, milliliters to cups, cubic meters to liters, and more. Volume conversion is used daily in cooking, chemistry, fuel measurement, and industrial processes. Common conversions: 1 gallon = 3.78541 liters, 1 liter = 1000 mL.
5. Area Conversion (sq ft to sq m, Acres, Hectares & More)
Convert square feet to square meters, acres to hectares, square kilometers to square miles, and more. Area conversion is essential in real estate, agriculture, architecture, and land surveying. Common conversions: 1 acre = 4046.86 sq meters, 1 hectare = 10,000 sq meters.
6. Time Conversion (Seconds, Minutes, Hours, Days & Weeks)
Convert hours to minutes, seconds to hours, days to weeks, and more. Time conversion is used in project management, programming, scientific calculations, and everyday scheduling. Common conversions: 1 hour = 3600 seconds, 1 day = 86,400 seconds, 1 week = 604,800 seconds.
How Unit Conversion Works — The Formula
Every unit conversion is based on a fixed mathematical ratio called a conversion factor. To convert a value, multiply it by the conversion factor of the source unit and divide by the conversion factor of the target unit:
Converted Value = (Input × Factor of From Unit) ÷ Factor of To Unit
Temperature conversions use dedicated formulas rather than simple ratios, since Celsius, Fahrenheit, and Kelvin scales have different zero points. Our calculator applies all standard conversion factors automatically, giving you precise results to four decimal places.
Metric vs. Imperial System — Key Differences
The metric system (SI) is the international standard used in science and by most countries worldwide. It is based on powers of 10, making conversions between units straightforward (e.g., 1 km = 1,000 m). The imperial system is used primarily in the United States and includes units like miles, pounds, gallons, and Fahrenheit. Converting between metric and imperial units —such as miles to kilometers or pounds to kilograms — is one of the most common real-world uses of a unit converter.
Common Unit Conversions Quick Reference
- 1 kilometer = 0.621371 miles
- 1 mile = 1.60934 kilometers
- 1 kilogram = 2.20462 pounds
- 1 pound = 0.453592 kilograms
- 0°C (Celsius) = 32°F (Fahrenheit) = 273.15 K
- 1 liter = 0.264172 gallons
- 1 acre = 0.404686 hectares
- 1 foot = 0.3048 meters
- 1 inch = 2.54 centimeters
- 1 hour = 3,600 seconds
Who Uses a Unit Conversion Calculator?
- Students & teachers — for physics, chemistry, math, and engineering homework
- Travelers — converting miles to km, °F to °C, or local currency units
- Cooks & bakers — switching between cups, liters, grams, and ounces in recipes
- Engineers & architects — converting area, length, and volume across systems
- Fitness enthusiasts — converting kg to lbs for bodyweight or equipment
- Real estate professionals — converting square feet to square meters or acres to hectares