Metric Units and Conversions

In short: Metric units go up in 10s, 100s and 1000s: 1 km = 1000 m, 1 kg = 1000 g and 1 L = 1000 mL. To change to a smaller unit, multiply, and to change to a bigger unit, divide. Time is different: it goes in 60s.

Before you start

• Multiplying and dividing by 10, 100 and 1000 (see the Number Skills unit).
• Fractions of an amount: divide by the bottom, multiply by the top.
• The prefixes: milli means one thousandth, centi means one hundredth, kilo means one thousand.

The key facts

Big to small: multiply

Small to big: divide

Fractions of a unit

Find the fraction of the bigger unit's number.

Time is not decimal

Area and volume units

A hectare is a square 100 m by 100 m, so it is $10000$ m². Farms and parks are measured in hectares.

$\frac{1}{4}$ ha $=2500$ m².

A box 5 cm by 7 cm by 10 cm has a volume of $5\times 7\times 10=350$ cm³, so it holds 350 mL of water.

Quick summary

• Metric units go up in 10s, 100s and 1000s.
• To change to a smaller unit, multiply. To change to a bigger unit, divide.
• 1 kg $=1000$ g, 1 L $=1000$ mL, 1 km $=1000$ m, 1 tonne $=1000$ kg, 1 m $=100$ cm.
• 1 hectare $=10000$ m², and 1 cm³ holds 1 mL.
• Time uses 60s: $1.5$ hours is 90 minutes, not 150.

Quiz