Free Universal Unit Converter — Fast Online Conversion
Convert instantly between units of length, weight, volume, area, speed, and temperature. Covers both metric (SI) and imperial/US customary units. Enter any value and see all equivalent units at once — no page reloads, no ads.
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Unit Converter
How to Use Unit Converter
- 1
Select the category: length, weight/mass, temperature, volume, area, or speed.
- 2
Enter your value in the source unit field.
- 3
All equivalent values in other units appear instantly.
- 4
Click any result to copy it to your clipboard.
- 5
Switch between metric and imperial groupings using the filter buttons.
Frequently Asked Questions
What unit categories are supported?▾
Length (mm, cm, m, km, inch, foot, yard, mile, nautical mile), weight/mass (mg, g, kg, tonne, oz, lb, stone), temperature (Celsius, Fahrenheit, Kelvin), volume (ml, L, m³, fl oz, cup, pint, quart, gallon), area (mm², cm², m², km², in², ft², acre, hectare), and speed (m/s, km/h, mph, knot).
How accurate are the conversions?▾
All conversions use the official SI-defined ratios and NIST values. Results are calculated to full floating-point precision. For most practical uses, 6 significant figures are displayed. Temperature conversions use the exact formulas (not rounded constants).
How do I convert Fahrenheit to Celsius?▾
Celsius = (Fahrenheit − 32) × 5/9. Example: 98.6°F = (98.6 − 32) × 5/9 = 37°C. To go the other way, Fahrenheit = Celsius × 9/5 + 32. The tool calculates this automatically — just type in either field.
How do I convert miles to kilometers?▾
1 mile = 1.60934 km exactly (by definition). To convert miles to km, multiply by 1.60934. Example: 26.2 miles (marathon) = 42.165 km. To convert km to miles, divide by 1.60934 (or multiply by 0.62137).
What is the difference between a US gallon and a UK gallon?▾
A US liquid gallon = 3.785 liters. A UK (imperial) gallon = 4.546 liters — about 20% larger. This matters for fuel economy: UK MPG figures are always higher than US MPG for the same car. Always check which gallon is being used when comparing international figures.
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