Unit Converter

How to use the converter

1. Type of measurement: pick a category. Only that category's units appear in the From and To lists.
2. Value: the number you want to convert.
3. From / To: the unit you have and the unit you need.

You also get the factor for one unit, such as 1 mi = 1.609344 km. Temperature has no single factor because the scales have different zero points, so that line shows a dash. For more units in a single category, use the dedicated converters: the weight converter adds carats, troy ounces and grains, the volume converter adds teaspoons, tablespoons, pints, quarts and oil barrels, the temperature converter adds Rankine, and the power converter handles watts, horsepower and BTU/h.

Definitions behind the factors

Each category converts through one SI base or derived unit: meter, kilogram, cubic meter, square meter, meter per second, second, pascal, joule and byte. Temperature goes through kelvin. Most factors are exact by definition:

• Length: 1 in = 2.54 cm, 1 ft = 0.3048 m, 1 mi = 1,609.344 m, 1 nautical mile = 1,852 m.
• Area: 1 acre = 4,046.8564224 m², based on the international foot, which since January 1, 2023 replaces the US survey foot; 1 ha = 10,000 m².
• Speed: 1 mph = 0.44704 m/s; 1 knot = 1 nautical mile per hour.
• Time: the year (yr) is the Julian year of 365.25 days, 31,557,600 s, the average length including leap years.
• Pressure: 1 bar = 100,000 Pa, 1 standard atmosphere = 101,325 Pa, 1 psi ≈ 6,894.757 Pa, 1 mmHg ≈ 133.322 Pa.
• Energy: 1 cal = 4.184 J (thermochemical calorie), 1 Wh = 3,600 J, 1 BTU ≈ 1,055.056 J (International Table BTU).
• Data: kB, MB, GB and TB are decimal (1 GB = 10⁹ bytes); KiB, MiB, GiB and TiB are binary (1 GiB = 2³⁰ = 1,073,741,824 bytes); 1 byte = 8 bits.

Results are rounded to 12 significant digits. The factor line is written out in full, with no exponent notation, even for very small factors: 1 s = 0.000000031688087814 yr.

Examples

1. Why a 500 GB drive shows less

Drive makers count in decimal gigabytes. Software that counts in binary units shows 500 GB as 465.66 GiB, often still labeled GB. A 1 TB drive is 931.32 GiB, or 0.91 TiB; a 256 GB phone holds 238.42 GiB. No space is missing, only the unit differs.

2. Driving abroad

100 km/h is 62.14 mph and 120 km/h is 74.56 mph; 70 mph is 112.65 km/h. A tire pressure of 32 psi equals 2.21 bar, and a European spec of 2.5 bar is 36.26 psi.

3. Land, homes and energy

Units that share a name

Several units exist in more than one version, and the label alone doesn't tell you which. The mile here is the statute mile; the nautical mile, used with knots, is 1.15 statute miles. The gallon is the US gallon; the imperial gallon is a separate option. The calorie is the thermochemical calorie of 4.184 J. A gigabyte can mean 10⁹ bytes or, in some software, 2³⁰ bytes. When precision matters, check which definition your source uses.