Unit Conversion Guide: Length, Weight and Temperature
Unit mix-ups have crashed spacecraft. For the rest of us they just cause recipe disasters and wrong measurements — here are the conversions worth knowing.
By ToolJolt Team · May 14, 2026
Length
- 1 inch = 2.54 cm (exact).
- 1 foot = 30.48 cm; 1 metre ≈ 3.28 feet.
- 1 mile ≈ 1.609 km; 1 km ≈ 0.621 miles.
Weight / mass
- 1 kg ≈ 2.205 pounds; 1 pound ≈ 0.454 kg.
- 1 ounce ≈ 28.35 grams.
- 1 stone = 14 pounds ≈ 6.35 kg.
Temperature
These need formulas, not factors. Celsius to Fahrenheit: F = C × 9/5 + 32. Fahrenheit to Celsius: C = (F − 32) × 5/9. Kelvin is Celsius + 273.15. A handy anchor: 37°C ≈ 98.6°F (body temperature) and −40° is the same in both scales.
Common mistakes
Confusing mass and force, mixing up US and UK gallons (they differ), and rounding too early in a chain of conversions are the usual culprits. When precision matters, keep full decimals until the final step.
Convert anything
ToolJolt's unit converter handles length, weight, temperature and many more categories instantly, so you never have to remember a factor again.
Free tools mentioned in this guide
Frequently asked questions
How many cm in an inch?
Exactly 2.54 centimetres. This is a defined value, not an approximation.
What is the formula to convert Celsius to Fahrenheit?
F = C × 9/5 + 32. To go back: C = (F − 32) × 5/9.
Are US and UK gallons the same?
No. A US gallon is about 3.785 litres and a UK (imperial) gallon is about 4.546 litres — a common and costly mix-up.