Unit Conversion Calculator
Use this unit conversion calculator to convert common measurements such as length, weight, volume, and temperature. This tool is useful for school, construction, travel, cooking, and everyday calculations.
Conversion Details
Result
Enter a value and click Convert.
How Unit Conversion Works
Unit conversion works by multiplying a known quantity by a conversion factor — the ratio that equals 1 when two equivalent measures are divided. To convert 5 kilometers to miles: 5 km × (0.621371 miles/km) = 3.11 miles. The conversion factor 0.621371 is exact by definition; any other multiplication would change the quantity, not just the label.
Temperature is the exception — it requires a formula rather than a simple multiplication, because Celsius and Fahrenheit have different zero points. °C to °F: multiply by 9/5, then add 32. °F to °C: subtract 32, then multiply by 5/9. Kelvin, used in science, starts at absolute zero (−273.15°C) and converts with simple addition/subtraction: K = °C + 273.15.
Commonly Needed Conversions
Length: 1 meter = 3.28084 feet | 1 mile = 1.60934 km | 1 inch = 2.54 cm. Weight: 1 kg = 2.20462 lbs | 1 pound = 16 ounces | 1 metric ton = 2,204.6 lbs. Volume: 1 liter = 0.264172 US gallons | 1 US gallon = 128 US fluid ounces = 3.78541 liters. Temperature: 0°C = 32°F, 100°C = 212°F, 37°C (body temp) = 98.6°F. Speed: 60 mph = 96.56 km/h | 100 km/h = 62.14 mph.
Frequently Asked Questions
What is the difference between mass and weight?
Mass is the amount of matter in an object and does not change with location — it is measured in kilograms or grams. Weight is the force that gravity exerts on that mass — it varies on the Moon or on a high mountain. In everyday use, people use "weight" and "mass" interchangeably because gravity is essentially constant at Earth's surface. Scientifically, when a scale displays "175 lbs" or "79.4 kg," it is measuring the gravitational force on your mass, which we conventionally call weight. The pound (lb) is actually a unit of force in the imperial system, while the kilogram is a unit of mass — this is why the two do not have a single universal conversion at all gravitational conditions, though on Earth's surface, 1 kg ≈ 2.20462 lbs.
How many liters are in a US gallon vs. an imperial gallon?
A US gallon equals 3.78541 liters. An imperial (UK) gallon equals 4.54609 liters — about 20% larger. This matters when interpreting fuel economy: a car that gets 40 mpg in the UK (imperial gallons) gets about 33.3 mpg in US gallons — a significant difference. When comparing fuel efficiency internationally, always confirm which gallon definition is being used. The US also uses smaller pints and quarts than the UK: a US pint is 16 fl oz (473 mL), while a UK pint is 20 fl oz (568 mL) — the reason a UK "pint of beer" is noticeably larger than a US pint.
Why does the US still use the imperial system?
The US, Liberia, and Myanmar are the only countries that have not officially adopted the metric system as the primary standard. The US attempted to transition in the 1970s (the Metric Conversion Act of 1975) but made it voluntary, and public adoption stalled. Industries that operate internationally — science, medicine, military, aviation, and pharmaceutical — already use metric. Consumer and construction sectors largely remain in imperial units due to inertia: tradespeople think in inches and feet, recipes use cups and tablespoons, and road signs show miles. Changing entrenched infrastructure and training costs is high, making complete transition politically difficult despite the technical simplicity of metric.