Every conversion.
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Fast, accurate and free unit converters for length, energy, pressure, frequency, and more.
What you will find here
Unit conversion exists because measurement systems grew in different places and eras. Metric units use decimal prefixes; imperial and US customary units still appear in height, body weight, cooking, and some engineering notes. SmartKitio converters apply published factors in your browser so you can move between systems without installing software.
Length & distance
Meters, feet, inches, kilometers, and miles—anchored on the exact inch definition of 25.4 mm.
Weight & mass
Kilograms, pounds, grams, and ounces using the international avoirdupois pound.
Temperature
Celsius, Fahrenheit, and Kelvin with the standard affine formulas (not a single multiply).
Area, volume & more
Area, volume (US liquid gallons unless a page says otherwise), speed, data, time, energy, pressure, power, angle, and frequency families.
Related guides
Read a longer explanation, then return to a tool when you need a result.
- Metric vs Imperial Units: Complete Guide
- How to Convert Kilograms to Pounds
- How to Convert Celsius to Fahrenheit
- Meters, Feet and Inches Explained
Popular Converters
Our most frequently used tools.
Length
Convert between metric lengths (millimeters to kilometers) and the international units used in the US and UK (inches, feet, yards, miles). Every unit is defined exactly in meters, so results are exact before rounding.
Weight
Convert mass between kilograms, grams, milligrams, pounds, and ounces. The pound and ounce are the international avoirdupois units, which are defined exactly in kilograms.
Temperature
Convert between Celsius, Fahrenheit, and Kelvin. Unlike most units, temperature scales have different zero points, so a conversion shifts by an offset as well as scaling.
Data
Convert digital storage sizes between bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes. This converter uses decimal (SI) prefixes, where 1 KB = 1,000 bytes.
Energy
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, and British thermal units, for example for food labels, electricity bills, or heating specifications.
m → ft
Convert meters (m) to feet (ft). One meter equals 3.28084 feet, so multiply a value in meters by 3.28084 to get feet.
km → mi
Convert kilometers (km) to miles (mi). One kilometer equals 0.621371 miles, so multiply a value in kilometers by 0.621371 to get miles.
kg → lb
Convert kilograms (kg) to pounds (lb). One kilogram equals 2.20462 pounds, so multiply a value in kilograms by 2.20462 to get pounds.
Explore Categories
Find exactly what you need by browsing our organized collections.
All Converters
Browse every converter by category, popularity, or name.
Celsius to Fahrenheit Converter
Convert degrees Celsius (°C) to degrees Fahrenheit (°F). The two scales start at different zero points, so the conversion uses a formula rather than a single factor: °F = °C × 9/5 + 32.
Data Converter
Convert digital storage sizes between bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes. This converter uses decimal (SI) prefixes, where 1 KB = 1,000 bytes.
Energy Converter
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, and British thermal units, for example for food labels, electricity bills, or heating specifications.
Kilograms to Pounds Converter
Convert kilograms (kg) to pounds (lb). One kilogram equals 2.20462 pounds, so multiply a value in kilograms by 2.20462 to get pounds.
Kilometers to Miles Converter
Convert kilometers (km) to miles (mi). One kilometer equals 0.621371 miles, so multiply a value in kilometers by 0.621371 to get miles.
Length Converter
Convert between metric lengths (millimeters to kilometers) and the international units used in the US and UK (inches, feet, yards, miles). Every unit is defined exactly in meters, so results are exact before rounding.
Meters to Feet Converter
Convert meters (m) to feet (ft). One meter equals 3.28084 feet, so multiply a value in meters by 3.28084 to get feet.
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin. Unlike most units, temperature scales have different zero points, so a conversion shifts by an offset as well as scaling.
Weight Converter
Convert mass between kilograms, grams, milligrams, pounds, and ounces. The pound and ounce are the international avoirdupois units, which are defined exactly in kilograms.
Acres to Hectares Converter
Convert acres (ac) to hectares (ha). One acre equals 0.404686 hectares, so multiply a value in acres by 0.404686 to get hectares.
Angle Converter
Convert angles between degrees, radians, gradians, and full turns. Negative angles are allowed because they describe rotation in the opposite direction.
Area Converter
Convert areas between square meters, square kilometers, hectares, square feet, square yards, and acres, for example for floor plans, land listings, or garden plots.
Celsius to Kelvin Converter
Convert degrees Celsius (°C) to kelvins (K). The two scales start at different zero points, so the conversion uses a formula rather than a single factor: K = °C + 273.15.
Centimeters to Inches Converter
Convert centimeters (cm) to inches (in). One centimeter equals 0.393701 inches, so multiply a value in centimeters by 0.393701 to get inches.
Fahrenheit to Celsius Converter
Convert degrees Fahrenheit (°F) to degrees Celsius (°C). The two scales start at different zero points, so the conversion uses a formula rather than a single factor: °C = (°F − 32) × 5/9.
Feet to Meters Converter
Convert feet (ft) to meters (m). One foot equals 0.3048 meters, so multiply a value in feet by 0.3048 to get meters.
Fluid Ounces to Milliliters Converter
Convert US fluid ounces (fl oz) to milliliters (mL). One US fluid ounce equals 29.5735 milliliters, so multiply a value in US fluid ounces by 29.5735 to get milliliters.
Frequency Converter
Convert frequency between hertz, kilohertz, megahertz, gigahertz, and revolutions per minute (RPM).
Gallons to Liters Converter
Convert US gallons (gal) to liters (L). One US gallon equals 3.78541 liters, so multiply a value in US gallons by 3.78541 to get liters.
Grams to Ounces Converter
Convert grams (g) to ounces (oz). One gram equals 0.035274 ounces, so multiply a value in grams by 0.035274 to get ounces.
Hectares to Acres Converter
Convert hectares (ha) to acres (ac). One hectare equals 2.47105 acres, so multiply a value in hectares by 2.47105 to get acres.
Inches to Centimeters Converter
Convert inches (in) to centimeters (cm). One inch equals 2.54 centimeters, so multiply a value in inches by 2.54 to get centimeters.
Kelvin to Celsius Converter
Convert kelvins (K) to degrees Celsius (°C). The two scales start at different zero points, so the conversion uses a formula rather than a single factor: °C = K − 273.15.
KM/H to MPH Converter
Convert kilometers per hour (km/h) to miles per hour (mph). One kilometer per hour equals 0.621371 miles per hour, so multiply a value in kilometers per hour by 0.621371 to get miles per hour.
Knots to KM/H Converter
Convert knots (kn) to kilometers per hour (km/h). One knot equals 1.852 kilometers per hour, so multiply a value in knots by 1.852 to get kilometers per hour.
Liters to Gallons Converter
Convert liters (L) to US gallons (gal). One liter equals 0.264172 US gallons, so multiply a value in liters by 0.264172 to get US gallons.
M/S to MPH Converter
Convert meters per second (m/s) to miles per hour (mph). One meter per second equals 2.23694 miles per hour, so multiply a value in meters per second by 2.23694 to get miles per hour.
Miles to Kilometers Converter
Convert miles (mi) to kilometers (km). One mile equals 1.60934 kilometers, so multiply a value in miles by 1.60934 to get kilometers.
Milliliters to Fluid Ounces Converter
Convert milliliters (mL) to US fluid ounces (fl oz). One milliliter equals 0.033814 US fluid ounces, so multiply a value in milliliters by 0.033814 to get US fluid ounces.
MPH to KM/H Converter
Convert miles per hour (mph) to kilometers per hour (km/h). One mile per hour equals 1.60934 kilometers per hour, so multiply a value in miles per hour by 1.60934 to get kilometers per hour.
MPH to M/S Converter
Convert miles per hour (mph) to meters per second (m/s). One mile per hour equals 0.44704 meters per second, so multiply a value in miles per hour by 0.44704 to get meters per second.
Ounces to Grams Converter
Convert ounces (oz) to grams (g). One ounce equals 28.3495 grams, so multiply a value in ounces by 28.3495 to get grams.
Pounds to Kilograms Converter
Convert pounds (lb) to kilograms (kg). One pound equals 0.453592 kilograms, so multiply a value in pounds by 0.453592 to get kilograms.
Power Converter
Convert power between watts, kilowatts, megawatts, and mechanical horsepower, for example for appliance ratings, engine output, or generator sizing.
Pressure Converter
Convert pressure between pascals, kilopascals, bar, atmospheres, psi, and millimeters of mercury, the units used for tire pressure, weather maps, and blood pressure readings.
Speed Converter
Convert speed between kilometers per hour, miles per hour, meters per second, and knots, whether for road speeds, physics problems, or marine and aviation speeds.
Square Feet to Square Meters Converter
Convert square feet (ft²) to square meters (m²). One square foot equals 0.092903 square meters, so multiply a value in square feet by 0.092903 to get square meters.
Square Meters to Square Feet Converter
Convert square meters (m²) to square feet (ft²). One square meter equals 10.7639 square feet, so multiply a value in square meters by 10.7639 to get square feet.
Time Converter
Convert durations between seconds, minutes, hours, days, and weeks. Each unit is a fixed number of seconds. Months and years are not included because their length varies.
Volume Converter
Convert liquid volume between liters, milliliters, cubic meters, and US customary units (gallons, quarts, pints, cups, and fluid ounces). The customary units here are US liquid measures, not UK imperial ones.