Unit converter for measurements, cooking and sizes
This unit converter changes a value from one unit to another in 20 measurement families. They include length, weight, temperature, volume, speed, data and fuel economy, plus cups to grams by density and shoe, ring and tire sizes. Each result names its units in full, such as US liquid gallon. The conversion runs in your browser.
Your result
Results use the displayed unit definitions. Copy copies the value; Download includes units, definitions and rounding notes.
How to convert units
Pick a family, type a value, choose the From and To units and select Convert. The page opens on 1 Meter to Foot (international), and changing any field clears the old result.
- Pick a Measurement family or a shortcut button: Length, Temperature, Cooking or Sizes. Sizes opens Shoe sizes. A new family fills in an example value.
- Type a number, or a tire size, in Value or size.
- Choose the From and To units. The swap button (⇄) reverses them and moves the current result into Value or size.
- For Cooking with density, fill in Ingredient density (g/mL).
- Set Display precision to 6, 10 or 15 significant digits. The default is 10.
- Select Convert, or press Enter in the value field. The answer appears under Converted value, with a summary line and a note.
- Select Copy result, or Download text to save unit-conversion.txt with the summary and note. Reset returns to Length and empties the value.
What Value or size accepts
Value or size takes a decimal number with a dot, such as 0.5 or 1250. A minus sign and e notation such as 1e3 also work. Commas, fractions and spaces between digits return an error, so type half a cup as 0.5 and one thousand as 1000.
Fuel economy and ring values must be greater than zero, and so must Ingredient density. Temperature takes negative values down to absolute zero. Shoe and clothing sizes take only chart values.
Tire size takes a size in place of a number. Type a metric size such as 205/55R16 or a flotation size such as 31x10.5R15. Extra text, such as the load index in 205/55R16 91V, returns a format error.
The field takes any number of digits, but the value must stay inside the browser's number range. For example, 1e999 meters returns a range error.
How each result is calculated
In most families each unit has a fixed conversion factor to a base unit. The converter multiplies your value by the From unit's factor and divides by the To unit's factor. One meter is 1 ÷ 0.3048 feet. At 10 significant digits that shows as 3.280839895, at 6 as 3.28084 and at 15 as 3.28083989501312.
Temperature adds an offset to the scale. 37 degrees Celsius becomes 37 × 9/5 + 32, which is 98.6 degrees Fahrenheit. A value below absolute zero, such as -300 °C, returns an error.
Fuel economy needs a division. Miles per gallon counts distance per unit of fuel, while liters per 100 km counts fuel per distance. So 30 miles per US gallon gives 7.840486111 L/100 km, and 30 miles per Imperial gallon gives 9.416031211 L/100 km.
The swap button carries a result back at 15 significant digits. After 37 °C to °F, swap puts 98.6 in the value field, and Convert gives 37 °C again.
US, Imperial and metric definitions
Gallons, quarts, pints, fluid ounces, cups and tablespoons come in more than one size, and the menu names the version of each. A US liquid gallon is 3.785411784 liters and an Imperial gallon is 4.54609 liters, so 1 US gallon is 0.8326741846 Imperial gallon. A US fluid ounce is 29.57352956 mL and an Imperial fluid ounce is 28.4130625 mL.
The menu shows the size of each cup. The US customary cup is 236.5882365 mL and the metric cup is 250 mL. A US tablespoon is 14.78676478 mL, a metric tablespoon is 15 mL and an Australian tablespoon is 20 mL.
The foot is the international foot of 0.3048 m, and the older US survey foot has its own entry. The inch, yard, mile and acre are the international versions based on that foot, with no survey mile or survey acre. The avoirdupois pound is 0.45359237 kg. Calories are thermochemical at 4.184 J, and mechanical horsepower is 745.6998716 W while metric horsepower is 735.49875 W.
Shoe, clothing, ring and tire sizes
Each size family follows one reference chart: Nike adult shoes, H&M Azerbaijan women's numeric clothing and Blue Nile US and Canada rings. A shoe or clothing size must match a chart value exactly, or the tool names the nearest entries and picks no size. UK 6 matches two US men's sizes, 6.5 and 7, so swap is off.
A ring measurement in millimeters gives a size only when exactly one chart entry rounds to what you typed. For example, 54 mm around gives US 7, and the summary shows the chart's 54.34955291 mm. At 17 mm across, US 6.5 at 16.9 mm and US 7 at 17.3 mm both round to 17, so the tool names both and picks no size.
Display precision is off for shoe, clothing and ring sizes, because the charts keep their own labels. Tire results give nominal width, diameter and circumference only, with no load rating, speed rating or fit advice.
Limits
The converter handles one value and one pair of units at a time. Results are decimal numbers, so it cannot give 5 ft 7 in or a fraction such as 3/8 inch. It has no conversion table. Very small and very large results use e notation, such as 1.653439153e-15 weeks for 1 nanosecond.
There is no currency, no pixels and no amps, volts or ohms, though Power and Energy cover watts and kilowatt-hours. Length has no micrometers, nanometers or light-years, and pressure has torr but no mmHg or inHg. Mass has no troy ounces, carats or grains, and volume has no US dry gallons or oil barrels.
Time has fixed durations up to weeks and a Julian year, with no months or time zones. Clothing has no S, M or L, and rings have no UK letter or EU sizes.
Questions
Which units can the converter handle?
It has 20 families: Length, Weight / mass, Temperature, Area, Volume, Speed, Pressure, Energy, Power, Torque, Data size, Data rate, Time, Angle, Fuel economy, Cooking with density, Shoe sizes, Clothing sizes, Ring size and Tire size. A conversion stays inside one family, and the Limits section lists missing units.
How do I convert between different units of measurement?
Multiply the value by a conversion factor, the number of target units in one source unit. For example, 5 feet times 0.3048 gives 1.524 meters. This online unit converter applies the factor for you once you pick a family, such as Length, and the From and To units. Temperature also needs an offset, because 0 °C is 32 °F.
How do I convert US or English units to metric?
English units are the US customary units and Imperial units. Put the English unit in From and a metric system unit in To, then select Convert. For example, 60 miles per hour gives 96.56064 kilometers per hour, and 1 inch gives 2.54 centimeters. Where the two differ, as gallons do, the menu lists both.
How do I convert cups to grams?
Select Cooking with density and enter your ingredient's density in grams per milliliter. The tool multiplies the volume by that density. At 0.5 g/mL, 1 metric cup of 250 mL gives 125 g, and 1 US customary cup gives 118.2941182 g. No single cup-to-gram figure fits every ingredient, so the density field is required.
Can I convert land area such as acres?
Yes. The Area family has acres, hectares, square miles, square yards, square feet, square inches and metric square units. One international acre is 43,560 square feet, or 4046.856422 square meters at 10 significant digits. One hectare is 2.471053815 acres, and one square mile is 640 acres.