1 kilogram = 1000 grams and 1 litre = 1000 millilitres. To change the small unit into the big unit, divide by 1000, because you need fewer of the bigger unit. To change the big unit into the small one, multiply by 1000. For a mixed amount like 2 kg 50 g, change the kilograms first (2000 g) and then add: 2050 g. As a decimal, 2050 g is 2.05 kg: the zero holds the tenths place.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- kilogram (kg)
- 1000 grams
- litre (L)
- 1000 millilitres
- mixed units
- an amount written with two units, like 2 kg 50 g
Worked examples
4000 g = ? kg
- 1.1000 g = 1 kg, so divide by 1000.
- 2.4000 ÷ 1000 = 4 kg.
= 4
2 kg 50 g = ? g
- 1.2 kg = 2000 g.
- 2.2000 + 50 = 2050 g.
= 2050
1750 mL = ? L
- 1.1000 mL = 1 L, so divide by 1000.
- 2.1750 ÷ 1000 = 1.75 L.
= 1.75
For parents
Method: Kilo means 1000
What to say: Is the new unit bigger or smaller? Should the number get bigger or smaller?
Common mistakes:
- Uses 100 instead of 1000 when changing between grams and kilograms or millilitres and litres.
- Multiplies when it should divide (or the reverse), so the number goes the wrong way.
- Writes a mixed measurement by putting the numbers side by side (2 kg 50 g → 250 g).
- Adds the two numbers of a mixed measurement without converting the larger unit.
- Treats the digits after the decimal point as a count of small units, losing the place-value zeros (1050 g → 1.50 kg; 2.35 kg → 2035 g).