Unit Converter: Convert Units Across 10 Categories

How to use the unit converter

1. Enter the numeric value you want to convert.
2. Select the category such as length, mass or temperature.
3. Choose the source unit in From and the target unit in To.
4. Read the converted result and the full reference table for every unit in that category.

How the unit converter works

This measurement converter uses exact conversion factors defined by international standards. For linear categories like length, mass and volume, each unit is stored as a ratio to a base unit. To convert units, the tool multiplies the input by the source factor and divides by the target factor.

For example, one mile equals exactly 1609.344 meters and one kilometer equals 1000 meters. Converting 1 mile to kilometers: 1 x 1609.344 / 1000 = 1.609344 km. Temperature uses formulas instead of simple ratios because the scales have different zero points. Celsius to Fahrenheit follows F = C x 9/5 + 32, so 100 degrees Celsius becomes 100 x 9/5 + 32 = 212 °F.

Exact conversion factors used

The unit conversion calculator relies on precise constants rather than rounded approximations. Below are selected factors used internally.

Pressure note: the mmHg here is the Torr, defined as exactly 1/760 of a standard atmosphere, so 1 atm is exactly 760 mmHg. The conventional mmHg (13595.1 kg/m3 mercury at standard gravity) is 133.322387415 Pa, which differs from the Torr by about one part in seven million and is irrelevant for everyday use.

Temperatures below absolute zero (0 K, -273.15 °C, -459.67 °F) are rejected because they cannot exist. The UK tablespoon is the old imperial unit (5/8 of an imperial fluid ounce); modern UK recipes use 15 mL.

Practical use cases

A general purpose unit converter saves time when working across systems. Engineers frequently switch between metric and imperial measurements for length, pressure and energy. Cooks converting recipes may need to go from US cups to milliliters or from ounces to grams. Scientists dealing with thermodynamics often move between Celsius, Kelvin and Fahrenheit.

Rather than searching for separate tools, this single page handles ten categories. If you need deeper detail for specific domains, dedicated calculators like the centimeters to inches converter or px to rem converter offer focused interfaces.

Common mistakes when converting units

The most frequent error is mixing up US and UK volume units. A US gallon is 3.785 liters while a UK (imperial) gallon is 4.546 liters, a difference of about 20 percent. Using the wrong gallon in a recipe or fuel calculation produces noticeably wrong results.

Another mistake is treating temperature like a linear unit. You cannot simply multiply Celsius by a factor to get Fahrenheit because the two scales start at different points. Always use the formula F = C x 9/5 + 32 or let this tool handle it.

Finally, confusing bits and bytes in data storage leads to eightfold errors. One byte equals eight bits, and network speeds are typically quoted in bits per second while file sizes use bytes.

Categories covered

This tool supports ten measurement families:

• Length: meter, kilometer, centimeter, millimeter, mile, yard, foot, inch, nautical mile.
• Mass: kilogram, gram, milligram, pound, ounce, metric ton.
• Temperature: Celsius, Fahrenheit, Kelvin.
• Volume: liter, milliliter, cubic meter, US gallon, US quart, US cup, US fluid ounce, UK tablespoon (old imperial), UK gallon.
• Area: square meter, square kilometer, hectare, acre, square foot, square inch.
• Speed: meters per second, kilometers per hour, miles per hour, knot, feet per second.
• Time: second, millisecond, minute, hour, day, week, year (365 days).
• Data: byte, kilobyte, megabyte, gigabyte, terabyte, bit, kibibyte, mebibyte, gibibyte.
• Pressure: pascal, kilopascal, bar, atmosphere, psi, mmHg (Torr).
• Energy: joule, kilojoule, calorie, kilocalorie, watt-hour, kilowatt-hour, electronvolt, BTU.

Worked examples