Online Unit Converter

The Online Unit Converter is a free, general-purpose conversion calculator covering 23 categories of measurement units commonly used in daily life, study, engineering and science, including length, weight, area, volume, speed, temperature, pressure, power, energy, data size, time, angle, frequency, force, torque, density, acceleration, electric current, voltage, resistance, data rate and fuel economy. No installation is required — just open the page to convert in real time on phones, tablets and computers.

Supported Categories

• Length: nanometer, millimeter, centimeter, meter, kilometer, inch, foot, yard, mile, nautical mile, Chinese li, chi, cun, zhang, light-year and more
• Weight: microgram, milligram, gram, kilogram, tonne, pound, ounce, carat, jin, liang
• Area & Volume: square meter, hectare, mu, acre; milliliter, liter, cubic meter, gallon, cup, tablespoon, teaspoon
• Temperature: Celsius, Fahrenheit and Kelvin with three-way conversion
• Physics & Engineering: pressure, power, energy, force, torque, density, acceleration, frequency, angle
• Electrical & Data: current, voltage, resistance, data size (B/KB/MB/GB/TB/PB), data rate (bps/Mbps, etc.)
• Time & Fuel Economy: milliseconds to years, plus L/100km, km/L, US/UK MPG

Key Features

• Instant conversion: results update as you type, with no button clicks required
• One-click swap: exchange the source and target units with the swap button
• Full comparison table: lists converted values for every unit in the current category, click any item to copy it
• Result copying: copy the main result or any value from the table for pasting elsewhere
• Scientific notation: very large or small numbers are shown in scientific notation with high precision
• Category deep links: open a specific category directly via a link parameter for easy sharing

How to Use

1. Select a category from the top bar, such as Length, Weight or Temperature
2. Enter a value and choose the source and target units
3. The result appears instantly, and the comparison table below updates with all units
4. Click "Copy" or any item in the table to copy the value

Who It's For

Ideal for students doing homework and experiments, engineers and technicians looking up conversions, shoppers and travelers converting measurements, cooking and baking volume conversions, fitness and diet calorie tracking, and any everyday scenario that needs a quick unit conversion.

FAQ

Q: Is this unit converter free to use?

A: Yes, completely free. All categories and units can be used unlimited times with no registration or payment.

Q: Are the conversion results accurate?

A: Conversions are based on internationally accepted standard factors and keep high-precision significant digits. Non-linear conversions such as temperature and fuel economy use dedicated formulas for reliable results.

Q: Which devices are supported?

A: Any device with a browser, including phones, tablets and computers. The layout adapts to the screen, and dropdowns are specially optimized for mobile.

Q: Can I see multiple unit results at once?

A: Yes. In addition to the main result, the "All units" table below lists the converted value for every unit in the current category for easy comparison.