Online Unit Converter & Conversion Calculators

Need to convert between units quickly and easily? Our free online unit converters help you switch between units of energy, power, pressure, temperature, volume, and more—without a formula sheet or manual calculations. Whether you’re an engineer checking a specification, a student solving a problem, or simply figuring out how many liters are in a gallon, these tools put conversions at your fingertips.

For unit conversions, enter a value, select your starting and target units, and get your result immediately. To explore the relationship between energy, power, and time, use the energy and power calculator.

Available conversion calculators

• Energy unit converter — Convert between joules, BTU, calories, kilowatt-hours, therms, and more.
• Energy and power calculator — Explore how energy, time, and power relate, with real-world comparisons involving gasoline, batteries, and steam.
• Diffusivity converter — Convert diffusivity and kinematic viscosity units, including stokes, cm²/s, and ft²/s.
• Force converter — Convert between newtons, pounds-force, dynes, kiloponds, and more.
• Mass converter — Convert between grams, kilograms, pounds, stones, tons, and other mass units.
• Power converter — Convert between watts, kilowatts, horsepower, BTU/hour, and more.
• Pressure converter — Convert between pascals, PSI, bar, atmospheres, and other pressure units.
• Temperature converter — Convert between Celsius, Fahrenheit, Kelvin, and Rankine.
• Viscosity converter — Convert between poise, pascal-seconds, centipoise, and other dynamic viscosity units.
• Volume converter — Convert between liters, gallons, cubic feet, barrels, and more.

Bookmark this page to keep these calculators handy. Check back for new tools as we expand our collection based on what visitors need.