Unit Conversion Calculator

Unit conversion is one of the most practically useful skills in everyday life — from international travel (miles to kilometers, Fahrenheit to Celsius) to cooking (cups to milliliters, pounds to grams), to construction and DIY projects (inches to centimeters, square feet to square meters). This calculator handles all major unit categories with precise, internationally standardized conversion factors.

All conversions in this calculator use exact or officially defined factors: the international yard is exactly 0.9144 meters, making the inch exactly 25.4 mm and the mile exactly 1,609.344 meters. Temperature conversions use the exact algebraic relationships between scales. There is no rounding in the conversion factors themselves — rounding only occurs in the displayed result.

Mental math shortcuts for the most common conversions: Miles to km: multiply by 1.6 (exact: 1.60934). Km to miles: multiply by 0.6 (exact: 0.62137). Pounds to kg: divide by 2.2 (exact: 0.453592). Kg to pounds: multiply by 2.2 (exact: 2.20462). Gallons to liters: multiply by 3.8 (exact: 3.78541). °C to °F: multiply by 1.8 and add 32. °F to °C: subtract 32 then divide by 1.8. Fluid ounces to milliliters: multiply by 30 (exact: 29.5735).

US vs. imperial (UK) measurements: US and UK both use "miles," "yards," and "feet" identically. Where they differ is in volume: the US fluid ounce (29.57 mL) differs from the UK fluid ounce (28.41 mL). The US gallon (3.785 L) differs from the UK gallon (4.546 L). When following UK recipes or fuel economy figures, always check which gallon is intended.

Scientific notation: for very large or very small quantities (astronomical distances, molecular sizes), scientific notation (e.g., 1.5 × 10⁸ km) is the standard format. Our calculator handles all practical everyday conversions within normal human-scale quantities.