Units of Mass: The Conversion Ladder, Table and Examples

Units of mass express how heavy an object is, with the kilogram as the base unit in the international system. The topic is taught in Years 3–4 and is used immediately in daily life: shopping at the market, weighing yourself, and following a recipe.

The Mass Conversion Ladder

From top to bottom:

kg → hg → dag → g → dg → cg → mg

There are only two rules:

• Every step down the ladder → multiply by 10
• Every step up the ladder → divide by 10

Worked Conversions

5 kg = ? g From kg to g is 3 steps down → 5 × 1,000 = 5,000 g

250 g = ? kg From g to kg is 3 steps up → 250 ÷ 1,000 = 0.25 kg

3.5 hg = ? dag One step down → 3.5 × 10 = 35 dag

Units Outside the Ladder

These are not on the ladder but appear constantly in word problems and at the market:

⚠️ Note: in Indonesia 1 ons = 100 grams, unlike the international ounce of roughly 28 grams. Schools and markets use the 100-gram value.

A Worked Word Problem

A shopper buys 2 kg of sugar, 5 ons of flour and 750 grams of eggs. What is the total in grams?

• 2 kg = 2,000 g
• 5 ons = 5 × 100 = 500 g
• Eggs = 750 g
• Total = 2,000 + 500 + 750 = 3,250 grams (or 3.25 kg)

The key to this kind of problem: convert everything to one unit first, then add.

The Mistakes That Actually Cost Marks

1. Multiplying and dividing the wrong way round. Dividing when going down, multiplying when going up. A hook that sticks: going down means smaller units, so the number gets bigger.

2. Miscounting the steps by one. Treating kg to g as two steps instead of three. Writing the ladder out before calculating removes this error entirely.

3. Knowing 1 ons is a tenth of a kg but forgetting it is also 100 g. Both are correct and identical, yet children often use different figures within one question.

4. Adding without converting first. Writing 2 kg + 500 g as 502, which means nothing.

5. Confusing quintals and tonnes. 1 quintal = 100 kg, 1 tonne = 1,000 kg. The tonne is the larger.

This ladder works exactly like the one for units of length, only the units differ. A child who understands one ladder understands them all — which means these are not three separate chapters but one.