Solo Biz Soft Editorial Team You do not always have a calculator to hand. These shortcuts give answers close enough for travel, cooking and DIY, and the exact figures show how accurate each one is.
The shortcuts
| Conversion | Shortcut | Example | Exact |
|---|---|---|---|
| km to miles | multiply by 0.6 | 100 km ≈ 60 mi | 62.14 mi |
| miles to km | multiply by 1.6 | 50 mi ≈ 80 km | 80.47 km |
| kg to pounds | double it, add 10% | 50 kg ≈ 110 lb | 110.2 lb |
| pounds to kg | halve it, subtract 10% | 150 lb ≈ 67.5 kg | 68.0 kg |
| inches to cm | multiply by 2.5 | 10 in ≈ 25 cm | 25.4 cm |
| cm to inches | multiply by 0.4 | 50 cm ≈ 20 in | 19.7 in |
| °C to °F | double, subtract 10%, add 32 | 20 °C ≈ 68 °F | 68 °F |
| °F to °C | subtract 30, halve | 70 °F ≈ 20 °C | 21.1 °C |
| liters to US gallons | divide by 4 | 20 L ≈ 5 gal | 5.28 gal |
| ml to fluid ounces | divide by 30 | 300 ml ≈ 10 fl oz | 10.1 fl oz |
When to be exact
Shortcuts are fine for road signs and weather, but not for medicine, engineering, baking or anything safety-related. Use exact converters like our unit converter for those.
Frequently asked questions
What is the easiest way to convert km to miles?
Multiply by 0.6. It is within about 4 percent.
How do I convert Celsius to Fahrenheit quickly?
Double it, subtract 10 percent, and add 32.
Are these shortcuts accurate?
They are approximations. Check the table for how close they are.
Related reading: How to Convert Celsius to Fahrenheit · How Many CM in an Inch
Shortcuts are estimates. Use exact conversions for critical work.