Unit Converters
Free, fast, accurate converters for everyday units. Type any value to see all equivalent measurements instantly. Both metric and imperial supported.
Length
Feet, meters, inches, centimeters, miles, kilometers, yards, millimeters
Weight
Kilograms, pounds, ounces, grams, stones, metric tons, US tons
Temperature
Fahrenheit, Celsius, Kelvin, Rankine
Volume
Liters, gallons (US/UK), cups, fluid ounces, milliliters, pints, quarts, tablespoons
Common conversions at a glance
The exact factors behind each converter above. Open any tool to convert your own value, or use these for quick mental math.
Length
- 1 inch = 2.54 cm
- 1 foot = 30.48 cm = 0.3048 m
- 1 mile = 1.609 km
- 1 meter = 3.281 feet
- 1 km = 0.6214 miles
Weight
- 1 kilogram = 2.205 pounds
- 1 pound = 453.6 g = 16 oz
- 1 ounce = 28.35 grams
- 1 stone = 14 pounds = 6.35 kg
- 1 metric ton = 1,000 kg
Temperature
- °F = (°C × 9/5) + 32
- °C = (°F − 32) × 5/9
- 0 °C = 32 °F (water freezes)
- 100 °C = 212 °F (water boils)
- 0 K = −273.15 °C (absolute zero)
Volume
- 1 US gallon = 3.785 liters
- 1 liter = 33.81 US fl oz
- 1 US cup = 236.6 mL = 8 fl oz
- 1 UK (imperial) gallon = 4.546 L
- 1 tablespoon = 14.79 mL
How unit conversion works
Almost every conversion on these pages is a single multiplication by a fixed factor. To go from a smaller unit to a larger one you divide (or multiply by a fraction); to reverse a conversion you use the reciprocal. For example, 1 inch is exactly 2.54 cm, so inches → cm multiplies by 2.54 and cm → inches divides by 2.54. Temperature is the one exception: because the Celsius and Fahrenheit scales start at different zero points, it needs a formula (°F = °C × 9/5 + 32) rather than a single factor.
The metric system (meters, grams, liters, Celsius) is base-10 and used by nearly every country. The US keeps imperial units (feet, pounds, gallons, Fahrenheit) for daily life while using metric in science, medicine, and the military, which is exactly why these converters get so much use. Each tool below shows every related unit at once, so you can read all equivalents from a single value.
Converter FAQs
What's the difference between US and imperial (UK) units?
They share names but differ in size for volume. A US gallon is 3.785 liters while a UK imperial gallon is 4.546 liters — about 20% larger. US and UK pints, cups, and fluid ounces differ for the same reason. Length and weight units (inches, feet, pounds) are identical in both systems. Our volume converter lets you pick US or UK explicitly.
How do I convert Celsius to Fahrenheit quickly?
Multiply the Celsius value by 1.8 and add 32. For a rough estimate, double the Celsius number and add 30 — close enough for weather. For example, 20 °C → exact is 68 °F, and the quick estimate gives 70 °F.
Are these conversions exact?
The defining factors are exact by international agreement: 1 inch is exactly 2.54 cm and 1 pound is exactly 453.59237 grams. Figures shown rounded here (like 2.205 lb per kg) are precise to the displayed digits; the converters themselves carry full precision and round only the final answer.