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Convert between hundreds of units — length, weight, temperature, and more.

Unit Converter

Convert between units of length, weight, area, volume, temperature, and speed

Understanding Unit Conversion

Unit conversion is the process of changing a measurement from one unit to another within the same category. The metric system (SI) is used globally and is based on powers of 10, making conversions straightforward. The imperial system, used primarily in the United States, uses non-decimal relationships that require memorized conversion factors.

Metric vs. Imperial Systems

The metric system uses base units (meter, kilogram, liter) with prefixes (kilo-, centi-, milli-) to scale by factors of 10. The imperial system uses units like feet, pounds, and gallons with irregular relationships (1 foot = 12 inches, 1 mile = 5280 feet). Temperature is unique — Celsius, Fahrenheit, and Kelvin each use different zero points and scale factors.

Common Conversion Factors

Some useful conversions to remember: 1 inch = 2.54 cm, 1 mile = 1.609 km, 1 pound = 0.4536 kg, 1 gallon = 3.785 liters, and 0°C = 32°F. For temperature, use the formula °F = °C x 9/5 + 32 or °C = (°F - 32) x 5/9. This converter handles all these calculations automatically with precise factors.

Common Mistakes

✗Confusing US gallons with imperial gallons (1 US gal = 3.785 L, 1 imperial gal = 4.546 L)
✗Applying simple multiplication for temperature instead of using the offset formula
✗Forgetting that area conversions require squaring the linear conversion factor

Pro Tips

✓Use the swap button to quickly reverse the conversion direction
✓For cooking conversions, memorize that 1 cup = 236.6 mL and 1 tablespoon = 14.8 mL
✓When traveling, remember 1 km is roughly 0.62 miles — a quick mental estimate

Real-World Examples

Travel distance

A 100 km drive in Europe is about 62 miles

Recipe conversion

200 grams of flour is approximately 7 ounces

Weather conversion

25°C is a comfortable 77°F room temperature

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Select a category and units, enter a value, and click Convert. Use the swap button to quickly reverse the conversion direction.

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Common Unit Conversions
Metric vs Imperial Systems

About Unit Converter

Common Unit Conversions

Unit conversion is the process of changing a measurement from one unit to another within the same category. Common conversions include length (1 mile = 1.609 km), weight (1 pound = 0.4536 kg), temperature (0°C = 32°F), and volume (1 gallon = 3.785 liters). This converter handles all these categories and more, using precise conversion factors for accurate results.

Temperature conversion is unique because it involves an offset in addition to a scale factor. Celsius to Fahrenheit uses the formula: °F = °C × 9/5 + 32. Kelvin is an absolute temperature scale where 0 K represents absolute zero, making it useful in scientific calculations. This converter handles all three temperature scales correctly.

Metric vs Imperial Systems

The metric system (SI) is the most widely used measurement system globally, adopted by nearly every country. It is based on powers of 10, making conversions simple—1 km = 1000 m, 1 m = 100 cm, 1 kg = 1000 g. The metric system is the standard in science, medicine, international trade, and most industries worldwide.

The imperial system (also called US customary units) is primarily used in the United States and a few other countries. It uses non-decimal relationships: 1 foot = 12 inches, 1 yard = 3 feet, 1 mile = 5280 feet. While less intuitive for calculations, imperial units remain common in everyday American life for height, weight, distance, and cooking measurements.

This utility is provided for informational purposes only. KnowKit is not responsible for any errors in the output.

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Frequently Asked Questions

How do I convert between metric and imperial units?

Multiply the value by the appropriate conversion factor. For example, to convert miles to kilometers, multiply by 1.609. To convert kilograms to pounds, multiply by 2.205. This converter handles all the math automatically — just select the units and enter a value.

Why is temperature conversion different from other units?

Unlike length or weight, temperature scales have different zero points, not just different scale factors. Celsius sets water's freezing point at 0°, Fahrenheit at 32°, and Kelvin at 273.15°. This means you need a formula with an offset: °F = °C x 9/5 + 32, not just a simple multiplier.

Are US gallons the same as imperial gallons?

No. A US gallon is 3.785 liters, while an imperial (UK) gallon is 4.546 liters — about 20% larger. This converter uses US gallons, which is the standard in the United States. Be aware of this difference when following recipes or instructions from different countries.

How accurate are the conversion factors used?

This converter uses precise, internationally recognized conversion factors. For example, 1 inch is exactly 2.54 cm by definition. Results are displayed with up to 8 decimal places to ensure precision for scientific and engineering use.

Can I convert area or volume between different unit systems?

Yes, this converter supports area (mm², cm², m², km², in², ft², yd², acres, hectares) and volume (mL, L, gallons, quarts, pints, cups, fluid ounces, tablespoons, teaspoons). Area and volume conversions use the squared or cubed linear conversion factors automatically.