How to Use This Unit Converter
Our unit converter supports four common measurement categories: length, weight, temperature, and volume. Simply select a category, choose your source and target units, enter a value, and get instant conversions with the formula displayed.
Steps:
- Select the measurement category (Length, Weight, Temperature, or Volume)
- Choose the unit you're converting from
- Enter the value you want to convert
- Choose the unit you're converting to (or use swap to flip them)
- View the converted result and formula instantly
Length Conversions
Length conversions are among the most commonly needed. The metric system uses millimeters, centimeters, meters, and kilometers, while the imperial system uses inches, feet, yards, and miles.
| From | To | Multiply By |
|---|---|---|
| 1 inch | centimeters | 2.54 |
| 1 foot | meters | 0.3048 |
| 1 yard | meters | 0.9144 |
| 1 mile | kilometers | 1.609344 |
| 1 meter | feet | 3.28084 |
| 1 kilometer | miles | 0.621371 |
Example: Convert 5 miles to kilometers: 5 × 1.609344 = 8.047 km
Weight Conversions
Weight conversions are essential for cooking, shipping, and fitness. The metric system uses milligrams, grams, kilograms, and metric tons, while the imperial system uses pounds and ounces.
| From | To | Multiply By |
|---|---|---|
| 1 pound (lb) | kilograms | 0.453592 |
| 1 ounce (oz) | grams | 28.3495 |
| 1 kilogram | pounds | 2.20462 |
| 1 gram | ounces | 0.035274 |
| 1 metric ton | kilograms | 1,000 |
Example: Convert 150 pounds to kilograms: 150 × 0.453592 = 68.04 kg
Temperature Conversions
Temperature conversion uses different formulas than simple multiplication because the scales have different zero points. The three main scales are Celsius, Fahrenheit, and Kelvin.
°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273.15| Celsius | Fahrenheit | Kelvin | Common Reference |
|---|---|---|---|
| 0°C | 32°F | 273.15 K | Water freezes |
| 37°C | 98.6°F | 310.15 K | Body temperature |
| 100°C | 212°F | 373.15 K | Water boils |
| −40°C | −40°F | 233.15 K | Equal point |
Example: Convert 72°F to Celsius: (72 − 32) × 5/9 = 40 × 5/9 = 22.2°C
Volume Conversions
Volume conversions are frequently needed in cooking and baking. The metric system uses milliliters and liters, while the US customary system uses gallons, quarts, pints, cups, and fluid ounces.
| From | To | Multiply By |
|---|---|---|
| 1 US gallon | liters | 3.78541 |
| 1 liter | US gallons | 0.264172 |
| 1 US cup | milliliters | 236.588 |
| 1 US fluid ounce | milliliters | 29.5735 |
| 1 US quart | liters | 0.946353 |
Example: Convert 3 gallons to liters: 3 × 3.78541 = 11.356 L
Frequently Asked Questions
What's the difference between US and imperial gallons?
A US gallon equals 3.78541 liters, while an imperial (UK) gallon equals 4.54609 liters — about 20% larger. This converter uses US customary units. Be careful when following older British recipes or measuring fuel efficiency.
Why is −40° the same in Celsius and Fahrenheit?
The two scales intersect at exactly −40°. You can verify this: −40 × 9/5 + 32 = −72 + 32 = −40. It's the only temperature where both scales read the same number.
Is a kilogram the same everywhere?
Yes. Since 2019, the kilogram is defined by the Planck constant, making it identical worldwide. The same applies to all SI units (meter, second, ampere, kelvin, mole, candela).
How do I convert between metric and imperial for cooking?
Common cooking conversions: 1 cup = 237 ml, 1 tablespoon = 15 ml, 1 teaspoon = 5 ml, 1 pound = 454 grams, 1 ounce = 28 grams. Our converter handles all of these and more.
What is absolute zero?
Absolute zero is 0 Kelvin (−273.15°C or −459.67°F), the theoretical lowest possible temperature where all molecular motion stops. It has never been achieved in practice, though scientists have gotten extremely close in laboratory settings.
Why does the converter show scientific notation for very small numbers?
For very small or very large results, scientific notation provides more readable precision. For example, 0.000001 meters is displayed as 1e-6, which is equivalent to 1 micrometer.