Unit Converter

Unit conversion is a daily need for students, engineers, scientists, cooks, and everyday users. Whether you are checking a recipe, sizing a woodworking project, converting a physics problem, or planning a road trip, the ability to switch between metric and imperial instantly saves time and prevents costly mistakes.

OpenToolLab's unit converter covers 220+ units across ten categories: length, weight, temperature, volume, area, speed, time, data, pressure, and energy. Instead of juggling ten separate calculators, you get one clean tool where every conversion lives in the same place and works the same way.

The metric↔imperial support is the feature most US users need most. Convert centimeters to inches for a design, kilograms to pounds for a fitness goal, Celsius to Fahrenheit for a weather report, or liters to gallons for a fuel tank — all with one click, no separate tools required.

Every conversion factor in this tool is sourced from SI standards, so results are accurate to ten significant figures. One inch is exactly 2.54 centimeters, one pound is exactly 0.45359237 kilograms, and the temperature formulas follow the standard °F = (°C × 9/5) + 32 and °C = (°F − 32) × 5/9. What you see here matches what you would get from a scientific reference.

Favorites and history are where this converter beats the generic alternatives. Save a conversion you use every week — like kg to lbs for a fitness log — as a favorite, and it appears as a one-tap chip. The history panel keeps your recent calculations so you can revisit a value without retyping. Both are stored in your browser's localStorage, which means they persist across visits and never leave your device.

Privacy is built into the architecture. There is no server processing your conversions, no account, and no tracking. Open the DevTools Network tab while you convert and you will see zero requests. That makes this tool safe for anything from homework to sensitive engineering data.

For engineers and scientists, the tool goes beyond the basics. Pressure units include pascal, bar, atmosphere, and PSI; energy includes joules, kilocalories, watt-hours, and BTU; data covers bits through petabytes. Students get the same depth — grams to kilograms, meters to kilometers, and millisecond to hour are all one click away.

Because the entire converter is a static page with no third-party scripts, it loads instantly and works offline. Bookmark it, install it as a PWA on your phone, and you have a full unit conversion toolkit that works everywhere — no signup, no ads, no data collection.