Unit Conversions Using Arithmetic
Every unit conversion is just a multiplication or division by the right conversion factor. Learn the factor and the calculation becomes trivial.
Length
| Conversion | Operation |
|---|---|
| km → m | × 1,000 |
| m → cm | × 100 |
| cm → mm | × 10 |
| m → km | ÷ 1,000 |
Mass
| Conversion | Operation |
|---|---|
| kg → g | × 1,000 |
| g → mg | × 1,000 |
| g → kg | ÷ 1,000 |
Capacity
| Conversion | Operation |
|---|---|
| litre → ml | × 1,000 |
| ml → litre | ÷ 1,000 |
Worked Examples
Example 1: 3.6 km in metres
3.6 × 1,000 = 3,600 m
Example 2: 2,500 g in kg
2,500 ÷ 1,000 = 2.5 kg
Imperial Conversions
| Imperial | Metric (approx.) |
|---|---|
| 1 mile | 1.609 km |
| 1 inch | 2.54 cm |
| 1 pound (lb) | 454 g |
| 1 pint | 568 ml |
Key Takeaways
- Smaller to larger unit: divide.
- Larger to smaller unit: multiply.
- Memorise the key conversion factors: 1000 (km/m, kg/g), 100 (m/cm), 10 (cm/mm).
Practice Questions
- Convert 4.7 km to metres.
- Convert 8,450 g to kilograms.
- Convert 2.3 litres to millilitres.
- A fence is 25.4 m long. How many 80 cm panels are needed?
- Convert 5 miles to km (use 1 mile ≈ 1.6 km).