Unit Converter

How to use this unit converter

Pick a category from the menu at the top (length, mass, temperature, and so on). Enter a number in either large field — the other side updates immediately. Use the unit dropdowns under each value to change meters to feet, kilograms to pounds, Celsius to Fahrenheit, or any other pair in that category. The shaded formula line explains the relationship for your current pair (multiply, divide, or a temperature rule). Expand Common conversions for a short cheat sheet of popular equivalents in that category.

Categories explained

Length is used for distance and size — from nanometres in chip design to light years in astronomy. Mass (often called weight in everyday speech) uses the kilogram as the SI anchor; carats and atomic mass units appear for gems and chemistry. Temperature needs offsets as well as scales, so Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur are linked by formulas, not a single multiplier. Volume separates liquid cooking measures (US cups, teaspoons) from litres and cubic metres. Area covers floors, land, and fields — including hectare and a practical Indian bigha reference (definitions vary by state). Speed includes km/h, mph, knots, and fixed references like Mach at sea level and the speed of light in vacuum.

Time spans nanoseconds to centuries; “month” and “year” use common averages because calendar months differ. Energy and power connect joules, calories, kilowatt-hours, and horsepower. Pressure maps pascals to PSI, bar, atmospheres, and millimetres of mercury. Data storage here uses binary kilo/mega/giga (powers of 1024), which matches how operating systems report file and RAM sizes. Frequency links hertz to RPM. Fuel economy ties together US mpg, Imperial mpg, km/L, and the inverse L/100 km style common in Europe. Angle uses radians as the mathematical base, with degrees, gradians, and arc minutes/seconds for surveying and astronomy.

Common conversions reference

Handy anchors: 1 inch = 2.54 cm exactly; 1 mile ≈ 1.609 km; 1 kg ≈ 2.2046 lb; 1 US gallon ≈ 3.785 L; 1 Imperial gallon ≈ 4.546 L; 0 °C = 32 °F; 100 °C = 212 °F; 1 hectare ≈ 2.471 acres. For digital sizes, 1 KiB = 1024 bytes (often shown as “KB” in software). For fuel, remember L/100 km drops as efficiency improves, while km/L and mpg rise.

Why metric vs imperial?

The metric system (SI) uses decimal prefixes and shared bases, which simplifies science, trade, and education. The US customary and British imperial systems persist in everyday life in several countries — road signs in miles, body weight in stones in the UK, US fluid ounces for recipes. Converters bridge the two without replacing local convention; precision matters when engineering or baking.

Precision and rounding

Factors and constants follow internationally used values (e.g. exact inch–centimetre definition). Displayed numbers are rounded for readability; very large or small results may use scientific notation. If you need legal or contract-critical figures, confirm against primary standards.

Why temperature is different

Most units are proportional: doubling the number doubles the physical quantity when converted. Temperature scales have different zeros and step sizes, so you cannot convert °C to °F by multiplying alone — you use a linear formula with an offset (and different handling for Kelvin as an absolute scale). That is why this tool shows explicit temperature rules in the formula box instead of a single “multiply by k” line.

Tips for students, cooks, and travellers

When doing homework, write the unit symbol beside every number until the final answer; this catches mismatched scales early. In the kitchen, liquid volumes differ between US cups and metric millilitres — pick the column that matches your recipe card. For travel, mentally anchor a few conversions (your height in feet, driving speed in mph, or luggage weight in pounds) so foreign signs feel less abstract. When you only need a rough estimate, rounding to two significant figures is often enough; when you are comparing prices per kilogram in a supermarket, one more digit helps. If two results disagree slightly, check whether one source used US definitions and another used imperial or metric — the labels on this page follow the definitions in the dropdowns.