Conversion Calculator

Convert units in one calculator

This unit conversion calculator handles ten common measurement categories without making you switch between separate tools. Select length, mass, temperature, volume, area, speed, pressure, energy, time, or digital data; enter a number; then choose the source and destination units. The result, reverse relationship, base-unit value, and a table of equivalent measurements update together.

How unit conversion works

Most conversions use a shared base unit. The calculator first converts the entered value to that base and then converts the base value to the requested unit. Length uses meters, mass uses kilograms, volume uses liters, area uses square meters, speed uses meters per second, pressure uses pascals, energy uses joules, time uses seconds, and digital data uses bytes.

result = entered value x source factor / destination factor

For example, one inch is exactly 0.0254 meter and one millimeter is 0.001 meter. Therefore, 1 inch x 0.0254 / 0.001 = 25.4 millimeters. Use the swap button to reverse the selected units while keeping the same entered value.

Length conversions

Length options include millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. The inch is defined as exactly 0.0254 meter, so a foot is exactly 0.3048 meter, a yard is exactly 0.9144 meter, and a mile is exactly 1,609.344 meters. These exact relationships support common searches such as inches to millimeters and the dedicated feet to meters calculator.

Mass and weight conversions

The mass category includes milligrams, grams, kilograms, ounces, pounds, stones, US short tons, and metric tonnes. One international avoirdupois pound is exactly 0.45359237 kilogram, one ounce is one-sixteenth of a pound, and one stone is 14 pounds. In everyday US and UK language, people often say weight when converting pounds or kilograms, even though mass and force are technically different physical quantities. For stone notation with leftover pounds, use the dedicated stones to pounds calculator.

Temperature conversion formulas

Temperature is different from linear unit conversion because Celsius, Fahrenheit, and kelvin do not share the same zero point. The calculator converts the entered temperature to Celsius, then converts Celsius to the target scale. Values below absolute zero are rejected.

F = C x 9 / 5 + 32
C = (F - 32) x 5 / 9
K = C + 273.15

Water freezes at 0 degrees Celsius, 32 degrees Fahrenheit, or 273.15 kelvins under the familiar reference condition. A temperature difference is not converted in exactly the same way as an absolute temperature, so this page is intended for absolute scale readings.

Volume conversions and the gallon warning

Volume options include milliliters, liters, cubic meters, US teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons, cubic inches, and cubic feet. The calculator labels the customary units as US units because an Imperial gallon is larger than a US gallon. One US liquid gallon is exactly 3.785411784 liters. One cubic inch is exactly 0.016387064 liter. For engine displacement or detailed equivalents, use the liters to cubic inches calculator.

Area conversions

Area factors are squared length factors. One square foot equals 0.09290304 square meter, but one foot equals 0.3048 meter; simply using 0.3048 for square feet would be incorrect. One acre is exactly 43,560 square feet, and one hectare is 10,000 square meters. The square feet to acres calculator can also estimate a rectangular lot from its dimensions.

Speed, pressure, and energy

Speed conversions include meters per second, kilometers per hour, miles per hour, feet per second, and knots. One mile per hour equals exactly 0.44704 meter per second. Pressure options include pascals, kilopascals, bar, pounds per square inch, standard atmospheres, and millimeters of mercury. Energy options include joules, kilojoules, thermochemical calories and kilocalories, watt-hours, kilowatt-hours, and British thermal units. Reference conditions and calorie or BTU definitions can vary in specialist work, so the labels identify the convention used by this calculator.

Time and digital data

Time options range from milliseconds through weeks and average Gregorian years. The average year used here is 365.2425 days; calendar years can contain 365 or 366 days. For calendar-style estimates, compare the assumptions in the weeks to months calculator. Digital data includes bits and bytes plus decimal kilobytes, megabytes, gigabytes, and terabytes, as well as binary kibibytes, mebibytes, gibibytes, and tebibytes. Decimal units use powers of 1,000; binary IEC units use powers of 1,024.

Accuracy, rounding, and authoritative factors

The calculator retains more precision internally than it usually displays. A long decimal result does not mean the original measurement was equally precise. Report only the significant digits supported by your input and purpose. The conversion factors are based on established SI relationships and the NIST Guide for the Use of the International System of Units. NIST notes that conversion-factor precision and rounding should match the intended application. Verify regulated, scientific, medical, safety-critical, or commercial measurements against the governing standard.

Frequently asked questions

Can I convert negative values?

Yes for meaningful signed quantities such as temperature. Negative values may be mathematically converted in other categories, but they may not represent a physically valid length, mass, area, or volume.

Why do US and metric results have many decimal places?

Exact definitions often produce terminating or repeating decimal results. The calculator shows enough digits for comparison while preserving the full value for subsequent calculations.

Are US fluid ounces the same as Imperial fluid ounces?

No. This calculator's teaspoon, tablespoon, fluid ounce, cup, pint, quart, and gallon choices are explicitly US customary units.

What is the difference between MB and MiB?

One decimal megabyte is 1,000,000 bytes. One mebibyte is 1,048,576 bytes. Storage vendors commonly use decimal units, while operating systems and technical tools may display binary quantities.