Metric to Imperial: A Quick Conversion Guide (with Formulas)
Switching between metric and imperial trips up almost everyone at some point. This guide gives you the exact formulas, a handy reference table, and a few mental-math shortcuts for when you don't have a converter open.
Length
- km → miles: × 0.621 (or roughly × 0.6). Shortcut: 100 km ≈ 62 miles.
- miles → km: × 1.609 (roughly × 1.6).
- cm → inches: ÷ 2.54.
- m → feet: × 3.281.
Weight
- kg → pounds: × 2.205 (roughly × 2.2). Shortcut: double it and add 10%.
- pounds → kg: ÷ 2.205.
- grams → ounces: ÷ 28.35.
Temperature
Temperature uses an offset, not just a multiplier:
- °C → °F: × 9/5, then + 32. Shortcut: double and add 30 for a rough figure.
- °F → °C: − 32, then × 5/9.
Handy anchors: 0 °C = 32 °F (freezing), 37 °C = 98.6 °F (body temp), 100 °C = 212 °F (boiling).
Volume
- litres → US gallons: ÷ 3.785.
- litres → UK gallons: ÷ 4.546 (note: UK and US gallons differ!).
- ml → fl oz (US): ÷ 29.57.
Quick reference
| Metric | ≈ Imperial |
|---|---|
| 1 km | 0.62 miles |
| 1 m | 3.28 feet |
| 1 cm | 0.39 inches |
| 1 kg | 2.2 pounds |
| 1 litre | 0.26 US gallons |
When precision matters
Mental shortcuts are great for estimates, but for recipes, engineering or shipping, use exact factors. Our unit converter uses precise, standards-based values and shows your number in every related unit at once — so you never convert twice.
FAQ
Why are UK and US gallons different?
They're historically separate units: 1 US gallon ≈ 3.785 L, 1 UK (imperial) gallon ≈ 4.546 L. Always check which one a recipe or spec means.
What's the easiest °C to °F trick?
Double the Celsius value and add 30 for a rough answer (exact is ×9/5 + 32).