Unit Converters
Quick daily-life calculators: dates, times, travel budgets, tips and currency conversions.
Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin instantly with the exact SI-defined formulas, showing all three scales at once.
Length Converter
Convert length between millimeters, centimeters, meters, kilometers, inches, feet, yards and miles using exact NIST/international definitions.
Weight Converter
Convert weight/mass between milligrams, grams, kilograms, tonnes, ounces, pounds and stone using exact avoirdupois definitions.
Speed Converter
Convert speed between kilometers per hour, miles per hour, meters per second and knots using exact SI and nautical-mile definitions.
Area Converter
Convert area between square meters, square kilometers, square feet, acres and hectares using exact NIST and international-foot definitions.
Volume Converter
Convert volume between milliliters, liters, cubic meters, US gallons, UK gallons, US cups and US fluid ounces with exact legal definitions.
Roman Numeral Converter
Convert numbers to Roman numerals or Roman numerals to numbers (1–3999), using standard subtractive notation with strict validation.
Energy Converter
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours, kWh, BTU, therms and foot-pounds using exact SI definitions.
Angle Converter
Convert angles between degrees, radians, gradians, turns, arcminutes, arcseconds and milliradians. Every factor is exact by definition.
Time Unit Converter
Convert a duration between milliseconds, seconds, minutes, hours, days, weeks, months and years, with the month and year definitions stated explicitly.
Unit Converter
Convert length, mass, volume, area and speed between metric and imperial units using the exact NIST conversion factors. One value in, every unit out.