Unit Converter
Instantly convert between 100+ units across 14 categories — length, weight, temperature, area, volume, speed, data, energy, pressure and more. Full conversion table, formula display, and history.
km = m × 0.001How to use the unit converter
Select a category from the tab bar at the top — Length, Weight, Temperature, and 11 more. Use the Quick shortcuts for the most common conversions (km→mi, kg→lb, °C→°F, etc.).
Choose your From and To units from the dropdowns, then type any value — the result updates instantly. Click the swapbutton to reverse the conversion. The result field becomes the new input.
The Conversion Table below the main converter shows your value expressed in every unit for the current category simultaneously. Click any row to select it as the new target unit. Adjust Decimal Places from 2 to 10 for the required precision.
Supported categories and units
Features
- 14 categories — length, weight, temperature, area, volume, speed, time, data, energy, pressure, power, angle, frequency, fuel economy
- 100+ individual units covering both metric and imperial systems
- Real-time conversion — results update as you type, no submit required
- Full conversion matrix — see all equivalent values for every unit at once
- Conversion formula display for every pair of units
- Precision control — 2 to 10 decimal places, automatic scientific notation
- One-click swap to reverse any conversion
- Popular quick shortcuts for the most searched conversions
- Click any matrix row to instantly set it as the output unit
- Conversion history saved in your browser (last 20 conversions)
- 100% client-side — works offline, no data sent to server
Frequently asked questions
How do I convert kilometers to miles?
Select the Length category, choose Kilometeras the From unit and Mile as the To unit. Enter your value and the result appears instantly. 1 kilometer = 0.621371 miles. You can also click the km → mi shortcut at the top.
How do I convert Celsius to Fahrenheit?
Select Temperature, choose Celsius → Fahrenheit. The formula is °F = (°C × 9/5) + 32. Common reference points: 0°C = 32°F, 100°C = 212°F, 37°C = 98.6°F (body temperature), −40°C = −40°F (they're equal at this point).
What is the difference between mass and weight?
Mass measures the amount of matter in an object (measured in kilograms) and doesn't change regardless of location. Weight is the gravitational force on that mass and varies by location. In everyday use the terms are used interchangeably — this converter uses the common convention where "weight" refers to mass units like kg, lb, and oz.
How does the conversion table work?
The conversion matrix shows your input value converted into every unit in the category simultaneously. The input unit is highlighted in purpleand the output unit in green. Click any row to select that unit as the new output — the main converter updates instantly.
How accurate are the conversion factors?
All factors are based on exact SI definitions. For example, 1 inch is exactly 0.0254 m (by international definition since 1959), 1 pound is exactly 453.592 g. Temperature conversions use exact formulas. You can increase precision up to 10 decimal places. Scientific notation activates automatically for very large or very small numbers.
How is L/100km (fuel economy) converted to MPG?
Fuel economy uses an inverse relationship — higher L/100km means lower efficiency (more fuel used per distance). The formula is: MPG (US) = 235.215 ÷ L/100km. For example, 8 L/100km ≈ 29.4 MPG US. UK MPG uses a different gallon size: MPG (UK) = 282.5 ÷ L/100km.
Does the converter work offline?
Yes. All conversion logic runs entirely in your browser using JavaScript. After the page loads once, conversions work without an internet connection. Conversion history is saved in your browser's localStorage and persists between sessions.