How do I convert between metric and imperial units?

Select the unit category (length, weight, etc.), choose the units you want to convert from and to, then enter a value. The conversion happens instantly. Common conversions: 1 inch = 2.54 cm, 1 mile = 1.609 km, 1 pound = 0.4536 kg, 1 gallon = 3.785 liters.

How many kilometers are in a mile?

One mile equals exactly 1.609344 kilometers. Conversely, one kilometer equals approximately 0.621371 miles. A quick mental trick: multiply miles by 1.6 to get approximate kilometers, or multiply kilometers by 0.6 to get approximate miles.

How many pounds are in a kilogram?

One kilogram equals approximately 2.20462 pounds. Conversely, one pound equals approximately 0.453592 kilograms. A quick estimate: multiply kg by 2.2 to get pounds, or divide pounds by 2.2 to get kilograms.

How many liters are in a gallon?

One US gallon equals approximately 3.78541 liters. One imperial (UK) gallon equals approximately 4.54609 liters. This calculator uses US gallons. To convert: multiply gallons by 3.785 to get liters, or divide liters by 3.785 to get gallons.

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Common Conversions

How Do You Convert Between Metric and Imperial Units?

To convert between metric and imperial units, multiply or divide by the appropriate conversion factor. This converter handles all calculations automatically — just select your units and type a value.

Key conversion factors: 1 inch = 2.54 cm, 1 mile = 1.609 km, 1 pound = 0.4536 kg, 1 gallon (US) = 3.785 liters, 1 acre = 4,047 m². Temperature conversions use formulas rather than simple multiplication: °F = °C × 9/5 + 32, and K = °C + 273.15.

How Do You Convert Celsius to Fahrenheit?

Multiply the Celsius temperature by 9/5 (or 1.8), then add 32. For example, 25°C = (25 × 1.8) + 32 = 77°F. To convert Fahrenheit to Celsius: subtract 32, then multiply by 5/9.

Key reference points: 0°C = 32°F (water freezes), 100°C = 212°F (water boils), 37°C = 98.6°F (body temperature), −40°C = −40°F (the point where both scales meet). Kelvin uses the same increments as Celsius but starts at absolute zero: 0K = −273.15°C.

What Is the Difference Between US and Imperial Gallons?

A US gallon equals 3.785 liters, while an Imperial (UK) gallon equals 4.546 liters — about 20% larger. This converter uses US gallons, which are standard in the United States.

The difference originates from different historical definitions. The US gallon is based on the wine gallon (231 cubic inches), while the Imperial gallon is based on the volume of 10 pounds of water. When converting recipes or fuel economy between US and UK sources, this difference matters significantly.

Note: Conversions use standard internationally recognized conversion factors. Temperature conversions use exact formulas. All values are calculated to high precision and displayed with up to 6 significant digits. US measurements are used for gallons, fluid ounces, cups, pints, and quarts.