Units of mass
Mass tells us how heavy something is. We use grams (g) for light things, such as a pencil or a spoon of sugar, and kilograms (kg) for heavier things, such as a bag of rice or a schoolbag.
There is only one fact to remember to swap between the two units, and then every question is either a multiply or a divide.
Key idea
1 kg = 1000 g.
Kilograms → grams: multiply by 1000. Grams → kilograms: divide by 1000.
Worked example
Worked example
A melon has a mass of 2 kg 500 g. How many grams is that?
2 kg = 2 × 1000 = 2000 g.
2000 + 500 = 2500 g.
Check: 2500 ÷ 1000 = 2.5 kg = 2 kg 500 g. Correct.
When you add or take away masses, add the grams to the grams and the kilograms to the kilograms. If the grams reach 1000, carry 1 kg.
Remember
- 1 kg = 1000 g.
- Heavier unit (kg) → lighter unit (g): multiply.
- Line up the units before you add or subtract.