The Ones Everyone Looks Up
| From | To | Quick approximation |
|---|---|---|
| 1 inch | cm | 2.54 cm |
| 1 foot | cm | ~30 cm |
| 1 kg | lbs | ~2.2 lbs |
| 1 lb | kg | ~0.45 kg |
| 0°C | °F | 32°F |
| 100°C | °F | 212°F |
Mental Math Shortcuts
KG to pounds: Double the kg number, then add 10%. 70kg → 140, plus 10% (14) → roughly 154 lbs (the real answer is 154.3, close enough for everyday use).
Celsius to Fahrenheit: Double the Celsius number and add 30. 20°C → 40 + 30 = 70°F (actual: 68°F — close enough to know if you need a jacket).
Miles to km: Multiply by 1.6, or roughly add 60% to the mile figure.
When You Need the Exact Number
Mental shortcuts are fine for a rough sense of scale, but for recipes, medication dosages, shipping weights, or anything where precision actually matters, use a real converter rather than rounding.
Try it now — nothing is ever uploaded.
Open convertci