Card 4 of 8
Units of measurement
Length, mass and capacity conversions — and the area trap that costs marks.
| Measure | Conversion | Rule |
|---|---|---|
| Length | 1 km = 1,000 m | ×1,000 |
| 1 m = 100 cm | ×100 | |
| 1 cm = 10 mm | ×10 | |
| 1 m = 1,000 mm | ×1,000 | |
| Mass | 1 kg = 1,000 g | ×1,000 |
| 1 tonne = 1,000 kg | ×1,000 | |
| Capacity | 1 litre = 1,000 ml | ×1,000 |
| 1 cl = 10 ml | ×10 | |
| Area | 1 m² = 10,000 cm² | ×100² (not ×100!) |
| Volume | 1 litre = 1,000 cm³ | 1 cm³ = 1 ml |
| Time | 1 hour = 60 min | ×60 |
| 1 min = 60 s | ×60 | |
| 1 day = 24 hours | ×24 | |
| 1 year = 365 days | 366 in a leap year |
The direction rule that prevents most errors: converting to a smaller unit means you need more of them → multiply. To a bigger unit → divide.
4,500 ml → litres. Litres are bigger → divide → 4.5 L ✓
The area trap. 1 m² is 10,000 cm², not 100. Because a square metre is 100 cm × 100 cm.