Convert between any units instantly. Length, weight, temperature, volume, speed, area, and more. Over 970 conversion tools.
Every unit conversion comes down to a fixed relationship between two measurements: one inch is exactly 2.54 centimeters by international definition, one kilogram is about 2.20462 pounds, one US liquid gallon is about 3.78541 liters. This directory organizes those relationships into more than 970 individual converter pages across nine categories — length, weight, temperature, volume, speed, area, data storage, time, and energy — plus printable reference tables for the conversions people look up most often. Each converter page takes any value you type and returns the converted result instantly, in your browser, with the full precision of the underlying factor rather than a rounded rule of thumb.
The ten popular converters listed above cover the conversions that come up in daily life: centimeters to inches for height and clothing sizes, kilograms and pounds for body weight and gym plates, Celsius and Fahrenheit for weather and oven temperatures, millimeters to inches for hardware and machining specs, kilometers to miles and miles per hour to kilometers per hour for travel and car dashboards, and gallons to liters for fuel and recipes. The tables section turns the same conversions into fixed charts you can scan — the centimeter table runs from 1 to 100, the weight and temperature tables list the everyday ranges, and the area table covers square feet to square meters for real estate and flooring work.
Length is the largest category and the simplest: every unit is a fixed multiple of the meter, so conversions are pure multiplication — divide by 2.54 for inches, by 25.4 for millimeters, multiply kilometers by 0.621371 for miles. Weight works the same way through the kilogram, with the pound fixed at 0.45359237 kg exactly. Area squares the length factors (one square foot is 0.0929030 square meters), and volume cubes them (one cubic foot is 28.3168 liters), which is why area and volume factors look less round than their linear cousins.
Temperature is the exception that needs two operations. Because Celsius and Fahrenheit zero points differ, the formula is multiply by 9/5 then add 32 in one direction, subtract 32 then multiply by 5/9 in the other. Kelvin, included in the broader converter set, shifts by a pure offset instead: 0 K is absolute zero at −273.15°C. Speed conversions combine length and time — miles per hour to kilometers per hour is just the mile factor of 1.609344 — and data storage runs on the binary ladder where each step multiplies by 1024 (kilobyte, megabyte, gigabyte, terabyte), though drive manufacturers use the decimal 1000 ladder, which is why a "1 TB" drive shows up as roughly 931 GiB in your operating system.
The table below collects the exact factors behind the popular converters in this directory. Every calculator on these pages uses the full-precision version of these numbers; the table shows them rounded for readability.
| Category | Converter | Exact relationship | Worked example |
|---|---|---|---|
| Length | cm to inches | 1 inch = 2.54 cm (exact) | 180 cm ÷ 2.54 = 70.87 in |
| Length | mm to inches | 1 inch = 25.4 mm (exact) | 100 mm ÷ 25.4 = 3.937 in |
| Length | km to miles | 1 mile = 1.609344 km (exact) | 10 km ÷ 1.609344 = 6.214 mi |
| Weight | kg to lbs | 1 kg = 2.20462 lbs | 75 kg × 2.20462 = 165.35 lbs |
| Temperature | °C to °F | °F = °C × 9/5 + 32 | 20°C × 1.8 + 32 = 68°F |
| Temperature | °F to °C | °C = (°F − 32) × 5/9 | (98.6 − 32) × 5/9 = 37°C |
| Volume | Gallons to liters | 1 US gal = 3.78541 L | 15 gal × 3.78541 = 56.78 L |
| Speed | MPH to km/h | 1 mph = 1.609344 km/h | 60 mph × 1.609344 = 96.56 km/h |
| Area | sqft to sqm | 1 sq ft = 0.0929030 sq m | 1000 sq ft = 92.90 sq m |
Most confusion in unit conversion comes from three systems overlapping. The metric system (SI) is decimal by design — every step is a power of ten, which is why metric conversions never need a lookup table beyond a prefix list. The US customary system descends from English units but has since diverged from the British imperial system in the units that matter most: the US liquid gallon (3.78541 L) is smaller than the imperial gallon (4.54609 L), the US pint and cup split differently, and only the inch-based length units remain identical because the inch has been defined as exactly 2.54 cm in both systems since 1959. Body weight is quoted in pounds (US) or stones (UK, 14 lbs each), which is why the weight converters here include stone and the length set includes hands-free everyday pairs like feet-and-inches to centimeters for height.
The practical rule this directory follows: converters default to US customary units, state which gallon, ton, or bushel they mean on the page, and always show the exact factor used so you can verify the result against a specification. For scientific and engineering work where the distinction between, say, the short ton (2000 lbs) and the metric tonne (1000 kg) changes the answer by ten percent, the category pages list each variant separately rather than guessing.
Use a converter when you have a specific number: the plumber's 3.4-meter pipe run, the 62.5 kg suitcase at the airline counter, the 195°F candy stage from a European recipe. Converters accept any decimal value and return the full-precision result instantly. Use a table when you're scanning rather than computing: checking what 170 cm means in feet and inches while reading a growth chart, or eyeballing a kilogram range while shopping for weights. Tables are also the better tool for learning a conversion — the pattern from 1 through 100 makes the scale stick in a way a single calculation doesn't. This directory pairs the two formats for the five most-used conversions — length, weight, temperature, speed, and area — so you can work either way without hunting for a second site.
Divide centimeters by 2.54 — the inch is defined as exactly 2.54 centimeters, so this conversion is exact, not approximate. 180 cm comes to about 70.87 inches. The cm to inches converter and its 1-to-100 table cover this end to end.
Multiply by 9/5 and add 32. Water freezes at 0°C / 32°F and boils at 100°C / 212°F. The offset exists because the scales have different zero points — unlike length conversions, you can't just multiply.
About 2.20462 pounds per kilogram; the pound is legally defined as 0.45359237 kg exactly. Multiply kg by 2.20462 for pounds, or divide pounds by 2.20462 for kilograms.
A US liquid gallon is 3.78541 liters; the imperial gallon used in the UK is 4.54609 liters. Always check which gallon a spec or recipe means — the difference is over 20%.
Drive makers use decimal units (1 TB = 1,000,000,000,000 bytes) while operating systems use binary units (1 TiB = 1,024⁴ bytes). The same bytes divided by the larger binary factor display as roughly 931 GiB. The data storage converters handle both ladders.