Convert between units of length, weight, volume, temperature, area, and more
This universal unit converter handles all common measurement types in one place. Whether you need to convert lengths for a DIY project, weights for shipping, volumes for cooking, or temperatures for travel, this tool provides instant, accurate conversions across metric, imperial, and specialized units.
The world uses two main measurement systems: metric (SI) used by most countries, and imperial/US customary units used primarily in the United States. Scientists, engineers, travelers, and anyone working internationally needs to move fluidly between these systems.
Our converter covers eight major categories—length, weight, volume, temperature, area, speed, time, and digital storage—with dozens of units in each category. Simply select your category, enter your value, choose your units, and get instant results.
Meters, feet, inches, miles, kilometers, yards, centimeters, millimeters, nautical miles.
Kilograms, pounds, ounces, grams, tons, stones, milligrams, micrograms.
Liters, gallons, cups, fluid ounces, milliliters, tablespoons, teaspoons, pints, quarts.
Celsius, Fahrenheit, Kelvin, Rankine. Essential for weather, cooking, and science.
| Conversion | Factor | Example | Category |
|---|---|---|---|
| Inches → Cm | × 2.54 | 12 in = 30.48 cm | Length |
| Pounds → Kg | × 0.4536 | 150 lb = 68 kg | Weight |
| Miles → Km | × 1.609 | 60 mi = 96.5 km | Length |
| Gallons → Liters | × 3.785 | 10 gal = 37.85 L | Volume |
| °F → °C | (°F-32)×5/9 | 98.6°F = 37°C | Temp |
| Ounces → Grams | × 28.35 | 8 oz = 227 g | Weight |
Know km↔mi for driving, °C↔°F for weather, and kg↔lb for luggage limits. Most countries use metric.
US recipes use cups/oz, international use grams/mL. 1 cup ≈ 240mL, 1 oz ≈ 28g.
Convert weights (lb↔kg) and distances (mi↔km) for international workout programs.
Convert between inches/feet and centimeters/meters. 1 inch = 2.54 cm exactly.
The US adopted the British Imperial system before the metric system became standard. While officially recognizing metric, the US never mandated conversion for everyday use. Cost, habit, and infrastructure keep imperial units in common use.
Both are equally accurate—they're just different scales. Metric is arguably easier for calculations because it's base-10 (1 km = 1000 m), while imperial has arbitrary relationships (1 mile = 5280 feet).
Use benchmarks: 1 inch ≈ 2.5 cm, 1 kg ≈ 2.2 lb, 1 mile ≈ 1.6 km, 1 liter ≈ 1 quart. For temperature: 0°C = freezing, 20°C = room temp, 37°C = body temp.
Reputable converters use exact conversion factors and are highly accurate. For critical applications (engineering, medicine), always verify with official conversion factors and consider significant figures.
A driver wants to convert a 5-mile distance into kilometers using the exact international mile definition.
Result8.04672 km
By the international yard and pound agreement of 1959, 1 mile equals exactly 1.609344 kilometers. Multiplying 5 by 1.609344 gives 8.04672 km. This factor is exact, so no rounding is introduced by the conversion itself.
The calculator covers eight categories: length, mass/weight, volume, temperature, area, speed, time, and digital storage. Within each category it supports the common SI units (meter, kilogram, liter, second), imperial and US customary units (mile, pound, gallon, fluid ounce), and a selection of specialised units such as nautical miles and metric tons.
SI is the International System of Units, the modern metric system maintained by the BIPM, with seven base units: meter, kilogram, second, ampere, kelvin, mole, and candela. Imperial and US customary units (foot, pound, gallon) are legacy systems still used mainly in the United States. SI is base-10 and used by virtually all of science, engineering, and global trade.
Several common conversions are defined as exact: 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 mile = 1.609344 km, and 1 US gallon = 3.785411784 L. Others, such as horsepower to watts or BTU to joules, depend on which definition is used and may differ slightly between standards. The calculator uses the exact factors wherever they are defined.
Compound units are converted by combining the factor for each base unit. To convert mph to km/h, multiply by 1.609344 because the time unit (hour) is the same on both sides. For units with different time bases, such as m/s to km/h, the converter scales the length factor and the time factor separately and combines them into a single ratio.
A few units share names but have different definitions. The US gallon (3.785 L) differs from the UK imperial gallon (4.546 L). A short ton (US) is 907.18 kg, while a long ton (UK) is 1016.05 kg and a metric tonne is exactly 1000 kg. The calculator distinguishes between these variants where they matter and labels them explicitly.
Temperature is not a simple ratio because Celsius, Fahrenheit, and Kelvin have different zero points. The calculator uses the standard formulas: K = C + 273.15, F = C times 9/5 + 32, and the inverse forms. Rankine is derived from Fahrenheit the same way Kelvin is derived from Celsius. These relationships are exact by definition.
Results are computed in full double precision and displayed with enough digits to preserve the input precision. For engineering or laboratory work, round the result to match the precision of your input value rather than the maximum digits shown. Exact conversion factors do not add uncertainty; only the input value does.
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