Everyday tools
Unit Converter
Convert between units of length, weight and mass, temperature, volume, area, speed and digital storage — all in one place. Pick a category, choose what you're converting from and to, type a value, and the answer updates instantly along with the exact conversion factor used. The United States runs on a mix of customary and metric units, so you constantly bounce between them: a recipe lists milliliters but your measuring cup shows fluid ounces, a European bolt is sized in millimeters but your wrench set is in inches, a weather app abroad reads in Celsius. This converter keeps inches, feet, miles, ounces, pounds, Fahrenheit, cups, gallons and miles per hour front and center, and it runs entirely in your browser with no network calls.
Convert a value
Choose units and enter a value
Most categories use a single multiplier; temperature also applies an offset.
Quick single-unit converters
Prefer a dedicated page for one conversion, with a reference table and worked example? Jump straight to the most-used pairs:
How the unit converter works
For length, weight, volume, area, speed and digital storage, every unit is defined relative to one base unit for its category (for example, the meter for length or the gram for mass). To convert, the tool first turns your value into the base unit, then turns the base value into your target unit. That two-step approach means a single multiplier — the conversion factor — does the whole job.
Linear conversion
result = value × (from base-factor ÷ to base-factor)where each unit's base-factor says how many base units it equals (1 inch = 0.0254 m)
Temperature is different because the scales don't share a zero point. Converting Celsius to Fahrenheit isn't just a multiply — you scale by 9/5 and then add 32. The tool handles °C, °F and Kelvin by first converting your value to Celsius, then to the target scale.
Temperature
°F = °C × 9/5 + 32 K = °C + 273.1550 °F → (50 − 32) × 5/9 = 10 °C
Notes & assumptions
- US fluid ounces, cups, pints, quarts and gallons are used (the US gallon is about 3.785 liters, smaller than the UK gallon).
- Weight units convert as mass; "ounce" here means the avoirdupois ounce, not the fluid ounce.
- Digital storage uses decimal units (1 KB = 1,000 bytes) plus binary KiB/MiB/GiB where labeled.
- Results are rounded for display but computed at full precision.
Master conversion factor table
These are the factors the tool applies under the hood, printed to four or five significant digits. Multiply by the factor to convert in the direction shown; multiply by the reverse factor to go back. The basis column gives the legal definition each factor comes from, so you can carry the full-precision number into a spreadsheet when the rounded one is not enough.
| Conversion | Multiply by | Reverse: multiply by | Basis |
|---|---|---|---|
| Length | |||
| cm → inches | 0.3937 | 2.54 | 1 in = 2.54 cm, exact |
| mm → inches | 0.03937 | 25.4 | 1 in = 25.4 mm, exact |
| meters → feet | 3.2808 | 0.3048 | 1 ft = 0.3048 m, exact |
| km → miles | 0.6214 | 1.6093 | 1 mi = 1,609.344 m, exact |
| Weight / mass | |||
| kg → pounds | 2.2046 | 0.45359 | 1 lb = 453.59237 g, exact |
| grams → ounces | 0.03527 | 28.350 | 1 oz = 28.349523125 g, exact |
| Volume (US) | |||
| liters → gallons | 0.26417 | 3.7854 | 1 gal = 231 cubic inches, exact |
| mL → fluid ounces | 0.03381 | 29.574 | 1 fl oz = 29.5735295625 mL, exact |
| cups → mL | 236.59 | 0.0042268 | 1 US cup = 236.5882365 mL, exact |
| Temperature | |||
| °C → °F | °F = °C × 9/5 + 32 | scale plus offset, not a factor | |
| °F → °C | °C = (°F − 32) × 5/9 | same formula reversed | |
| Speed | |||
| km/h → mph | 0.6214 | 1.6093 | same 1,609.344 m mile as length |
A pattern worth noticing: km to miles and km/h to mph share the factor 0.6214, because a speed conversion is just the length conversion applied per hour. Any factor pair in the table multiplies to 1 at full precision; 2.54 × 0.3937 lands at 0.999998, a hair under 1, only because 0.3937 is the rounded display of 0.39370078740.
Which conversions are exact
Since the international yard and pound agreement of 1959, US customary length and weight units have had exact metric definitions: 1 inch = 2.54 cm, 1 foot = 0.3048 m, 1 mile = 1,609.344 m, and 1 pound = 453.59237 g. Volume inherits that exactness, because the US gallon is defined as 231 cubic inches, which works out to exactly 3.785411784 liters, and the US cup, half a US pint, is exactly 236.5882365 mL. When this tool converts inches, pounds, gallons or cups, the arithmetic is exact and the only rounding happens in the digits shown on screen.
What is not exact: anything that depends on a physical property instead of a definition. Turning a cup of flour into grams requires the flour's density (about 120 g per cup for all-purpose, but it varies with how you scoop), which makes it a measurement, not a conversion. Ingredient charts, nutrition estimates and fuel economy comparisons all live in that bucket. Also watch for regional unit families that share a name: the imperial UK gallon is exactly 4.54609 liters, a genuinely different unit from the US gallon rather than a rougher version of it.
Worked example
Suppose a European furniture listing says a desk is 120 centimeters wide and you want feet. Choose Length, set From to centimeters and To to feet, and enter 120: the tool converts 120 cm to 1.2 m, then divides by 0.3048 m per foot to get about 3.94 feet. Now say a runner abroad ran 10 kilometers and you think in miles — switch From to kilometers, To to miles, enter 10, and you get roughly 6.21 miles. For cooking, a cake recipe calling for 250 milliliters of milk is about 1.06 US cups. And if a forecast in Madrid reads 30 °C, the Temperature category turns it into a balmy 86 °F. The conversion factor shown under each result lets you reuse the same multiplier for similar conversions without reopening the tool.
Second worked example: converting a whole recipe
An American brownie recipe travels badly to a metric kitchen, and it makes a good stress test because one recipe crosses three categories. The oven line reads 350 °F: temperature math gives (350 − 32) × 5/9 = 176.7 °C, so you set the closest dial mark, 175 or 180 °C. The 2 cups of milk go through volume: 2 × 236.588 = 473.2 mL, just under half a liter. The 8 ounces of chocolate go through weight: 8 × 28.3495 = 226.8 grams, which a kitchen scale will read as 227.
Notice that each line needed its own factor, and the temperature line needed a formula rather than a factor at all. That is the whole trick to converting anything confidently: identify the category first, then apply its one rule. Run each line through the matching category above and the recipe comes out the same on either side of the Atlantic.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (that's 1.8) and add 32. So 20 °C is 20 × 1.8 + 32 = 68 °F. To go the other way, subtract 32 first, then multiply by 5/9: 50 °F becomes (50 − 32) × 5/9 = 10 °C. Unlike length or weight, temperature needs that "+32" offset because the two scales don't start at the same zero.
Is a US gallon the same as a UK gallon?
No. This converter uses US customary units, where one gallon is about 3.785 liters, four quarts, eight pints or 128 fluid ounces. The imperial (UK) gallon is larger, roughly 4.546 liters. The US fluid ounce and cup are also slightly different sizes from their imperial counterparts, so always confirm which system a recipe or spec sheet is using.
How many feet are in a meter?
One meter equals about 3.281 feet, because a foot is defined as exactly 0.3048 meters. Put another way, one foot is 12 inches and each inch is exactly 2.54 centimeters. For quick mental math, a meter is "a yard plus a few inches," which is close enough for rough estimates but not for precise work.
How do I convert kilograms to pounds?
Multiply kilograms by 2.2046. A 70 kg suitcase weighs 70 × 2.2046 = 154.3 pounds, past the 50 lb airline limit three times over. The factor comes from the legal definition of the pound as exactly 453.59237 grams, so the conversion itself is exact and only the displayed digits are rounded. To go from pounds back to kilograms, multiply by 0.45359 instead.
How many milliliters are in a cup?
One US cup is 236.588 mL, defined as exactly half a US pint. Recipes from Australia and New Zealand usually mean a 250 mL metric cup, and older UK cookbooks may mean the 284 mL imperial half pint, so check where a recipe comes from before you measure. When a recipe is written in milliliters, the safest move is to measure in milliliters directly.
Why is the conversion factor shown?
Seeing the exact multiplier lets you sanity-check the result and reuse it. If converting miles to kilometers shows a factor of about 1.609, you can confidently multiply any mileage by 1.609 in your head or on paper. For temperature there is no single factor because of the offset, so the tool shows the scale-and-shift formula instead.
Does digital storage use 1,000 or 1,024?
It depends on the unit. Decimal units — KB, MB, GB, TB — step by 1,000, which is how drive manufacturers and most networks label capacity. Binary units — KiB, MiB, GiB — step by 1,024 and are what operating systems often report. This converter includes both so you can match whichever your device is using.
Are these conversions exact?
The underlying definitions are exact (an inch is exactly 2.54 cm, a pound is exactly 453.59237 grams), but the displayed answer is rounded for readability. Calculations run at full floating-point precision behind the scenes, so for everyday cooking, travel and DIY the results are accurate. For laboratory or engineering work, use the documented exact factor.