Weight in kilograms and grams

A grain of rice is light. A bag of cement is heavy. To compare weights, we use standard units: the kilogram (kg) for heavier things and the gram (g) for lighter ones.

What is this?

The kilogram and gram are related by a friendly factor of 1,000:

$1 \text{ kg} = 1{,}000 \text{ g}$

So:

• 2 kg = 2,000 g
• 500 g = $\frac{1}{2}$ kg = 0.5 kg
• 1 kg 250 g = 1,250 g

We use kilograms for things like rice, wheat, vegetables, our own body weight. We use grams for spices, gold, chocolate, medicines.

To go from kg to g, multiply by 1,000. To go from g to kg, divide by 1,000.

When weights are given in mixed units like "2 kg 350 g", we can either add unit by unit or convert everything to grams.

For example, 2 kg 350 g + 1 kg 800 g:

• Combined as kg: 3 kg.
• Combined as g: 350 + 800 = 1,150 g = 1 kg 150 g.
• Total: 3 kg + 1 kg 150 g = 4 kg 150 g.

If the g total crosses 1,000, we carry over 1 kg.

Worked examples

Example 1. Convert 3 kg 250 g to grams.

• 3 kg = 3,000 g.
• 3,000 + 250 = 3,250 g.

Example 2. A shopkeeper weighs 1 kg 800 g of dal and 2 kg 600 g of rice. Total weight?

• 1 kg 800 g + 2 kg 600 g.
• g: 800 + 600 = 1,400 g = 1 kg 400 g.
• kg: 1 + 2 + 1 = 4 kg, 400 g left.
• Total = 4 kg 400 g.

Example 3. A packet of biscuits weighs 250 g. How many packets make 2 kg?

• 2 kg = 2,000 g.
• 2,000 ÷ 250 = 8 packets.

Try it

1. Convert 4 kg 750 g to grams.
2. Convert 3,250 g to kg and g.
3. Add: 2 kg 450 g + 1 kg 700 g.
4. Subtract: 5 kg − 2 kg 380 g.
5. A packet of sugar weighs 500 g. How many packets in 4 kg?

Hands-on

Kitchen scales. With a weighing scale at home, weigh 5 different items in the kitchen. Note each in kg and g. Predict which is heavier before checking.

Shop list. Make a small grocery list with at least 5 items, each with a weight (250 g sugar, 1 kg rice, etc.). Add up all the weights. How much in kg?