📖 Quick Reference
Length
- 1 inch = 2.54 cm
- 1 foot = 30.48 cm = 12 inches
- 1 mile = 1.609 km
- 1 meter = 3.281 feet
Weight
- 1 pound = 453.6 grams = 16 ounces
- 1 kilogram = 2.205 pounds
- 1 stone = 14 pounds = 6.35 kg
Volume
- 1 gallon (US) = 3.785 liters
- 1 cup = 236.6 ml
- 1 fluid ounce = 29.57 ml
Temperature
- °F = (°C × 9/5) + 32
- °C = (°F - 32) × 5/9
- K = °C + 273.15
❓ Frequently Asked Questions
The US uses US Customary units (based on British Imperial), while most of the world uses the metric system. The US attempted to switch in the 1970s but it never fully adopted.
US gallon = 3.785 liters. UK (Imperial) gallon = 4.546 liters. The UK gallon is about 20% larger!
Quick estimate: Double the Celsius, then add 30. (20°C → 40 + 30 = 70°F). Actual: 68°F. Close enough for casual use!
Kelvin starts at absolute zero (no negative numbers), making it ideal for scientific calculations. 0 K = -273.15°C, the coldest possible temperature.