What is a Unit Converter?
A unit converter is a tool that converts measurements from one unit to another within the same category — such as kilometers to miles, kilograms to pounds, or Celsius to Fahrenheit. Unit conversion is needed in science, cooking, travel, engineering, medicine, and many everyday situations where measurements from different systems need to be compared or communicated.
Our free unit converter supports 7 major categories with dozens of units, covering the most common conversion needs for students, professionals, and everyday users worldwide.
The Two Major Measurement Systems
- Metric System (SI): Used by most of the world. Based on powers of 10. Units: meter, kilogram, liter, Celsius, etc.
- Imperial System (US Customary): Used primarily in the United States. Units: foot, pound, gallon, Fahrenheit, etc.
Quick Conversion Reference
- 1 kilometer = 0.621 miles | 1 mile = 1.609 kilometers
- 1 kilogram = 2.205 pounds | 1 pound = 0.454 kilograms
- 0°C = 32°F | 100°C = 212°F | Formula: °F = (°C × 9/5) + 32
- 1 liter = 0.264 US gallons | 1 US gallon = 3.785 liters
- 1 hectare = 2.471 acres | 1 acre = 0.405 hectares
- 1 meter/second = 3.6 km/h = 2.237 mph
- 1 gigabyte = 1024 megabytes = 1,073,741,824 bytes
Frequently Asked Questions
How accurate are the conversion results?+
Our converter uses precise conversion factors and calculates results to 10 significant figures. Results are displayed without unnecessary trailing zeros. For scientific or engineering work requiring extreme precision, verify with official standards (NIST or ISO), but for all everyday purposes, our results are accurate.
Why is temperature conversion different from other conversions?+
Unlike length or weight, temperature scales do not have a common zero point, so you cannot simply multiply by a constant factor. Celsius and Fahrenheit have different zero points (water freezes at 0°C vs 32°F) and different scale increments. Kelvin starts at absolute zero (-273.15°C). This requires a two-step formula: adjust for the offset, then scale.
What is the difference between a US gallon and an Imperial gallon?+
A US gallon = 3.785 liters, while a UK Imperial gallon = 4.546 liters. They are significantly different — about 20% apart. Our converter uses US gallons. If you need UK Imperial gallons, note that 1 Imperial gallon = 1.201 US gallons.
What is absolute zero in temperature?+
Absolute zero is the lowest theoretically possible temperature — the point at which all molecular motion stops. It equals 0 Kelvin, -273.15°C, or -459.67°F. The Kelvin scale starts at absolute zero, making it the most useful scale for scientific calculations involving temperature ratios.