Length is measured in millimetres (mm), centimetres (cm), decimetres (dm), metres (m), decametres (dam), hectometres (hm) and kilometres (km).

Key Relationships

• 1 m = 100 cm = 1000 mm
• 1 km = 1000 m
• 1 dam = 10 m
• 1 hm = 100 m

Converting Large Units to Small Units (multiply)

When you convert from a larger unit to a smaller unit, you multiply.

Example: Convert 3 km into metres

1 km = 1000 m

3 km = 3 × 1000 m = 3000 m

So, 3 kilometres equals 3000 metres.

Example: Convert 7 m into centimetres

1 m = 100 cm

7 m = 7 × 100 cm = 700 cm

Converting Small Units to Large Units (divide)

When you convert from a smaller unit to a larger unit, you divide.

Example: Convert 500 cm into metres

100 cm = 1 m

500 cm = 500 ÷ 100 = 5 m

Example: Convert 4500 m into kilometres and metres

First, split into complete thousands: 4500 m = 4000 m + 500 m

4000 m = 4000 ÷ 1000 = 4 km

So, 4500 m = 4 km 500 m

Mass is measured in milligrams (mg), centigrams (cg), decigrams (dg), grams (g), decagrams (dag), hectograms (hg), kilograms (kg) and tonnes (t).

Key Relationships

• 1 kg = 1000 g
• 1 g = 1000 mg
• 1 tonne = 1000 kg

Converting Large Units to Small Units (multiply)

Example: Convert 4 kg into grams

1 kg = 1000 g

4 kg = 4 × 1000 g = 4000 g

Converting Small Units to Large Units (divide)

Example: Convert 7000 g into kilograms

1000 g = 1 kg

7000 g = 7000 ÷ 1000 = 7 kg

Example: Convert 2 tonnes into kilograms

1 tonne = 1000 kg

2 tonnes = 2 × 1000 kg = 2000 kg

Converting Between Milligrams and Tonnes

Example: Convert 5,000,000 mg into kilograms

First, convert mg to g: 1 g = 1000 mg

5,000,000 mg = 5,000,000 ÷ 1000 = 5000 g

Then convert g to kg: 1 kg = 1000 g

5000 g = 5000 ÷ 1000 = 5 kg

So, 5,000,000 mg = 5 kg

Volume is measured in millilitres (mL) and litres (L).

Key Relationship

• 1 litre = 1000 millilitres

Converting Litres to Millilitres (multiply)

Example: Convert 9 litres into millilitres

1 L = 1000 mL

9 L = 9 × 1000 mL = 9000 mL

Converting Millilitres to Litres (divide)

Example: Convert 18000 mL into litres

1000 mL = 1 L

18000 mL = 18000 ÷ 1000 = 18 L

• To convert large unit to small unit: multiply by the conversion factor
• To convert small unit to large unit: divide by the conversion factor
• Remember: kilometre, kilogram and kilolitre are the largest units
• Remember: millimetre, milligram and millilitre are the smallest units

1. Always know the conversion factor (how many of the smaller unit make 1 of the larger unit)
2. When converting multiple steps, convert one step at a time
3. Check your answer by reversing the conversion

In Tanzania, these conversions are used in many daily activities. For example, when a farmer sells maize at the market, the buyer may ask for 500 kilograms but the farmer's scale shows 0.5 tonnes — the farmer must convert 0.5 tonnes to 500 kilograms to confirm the correct amount. Similarly, when buying cooking oil in a shop, the label might show 500 mL, but you need to know this is equal to half a litre to compare prices with a 1-litre bottle.