1 kilometre is 1000 metres. That is a rate, exactly like 3 pens for £1.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Which way round
Going to a smaller unit gives a bigger number, so multiply. Going to a bigger unit, divide.
A check that always works
5 km in metres should be far more than 5. If your answer is smaller, you divided when you should have multiplied.
Nothing is added
5 km and 5000 m are the same distance. Only the unit changed.
A conversion factor is a rate equal to one
100 cm per 1 m is a rate, and because 100 cm and 1 m are the same length, that rate equals 1. Multiplying by it changes the unit without changing the amount — which is exactly what a conversion needs to do.
Let the units cancel
To convert 3 m to centimetres, write 3 m × (100 cm / 1 m). The metres cancel, leaving 300 cm. Tracking units through the calculation tells you whether to multiply or divide, so you never have to guess the direction.
Chaining conversions
To convert 5 km to centimetres, go through metres: 5 km × (1000 m / 1 km) × (100 cm / 1 m) = 500,000 cm. Each factor cancels one unit and introduces the next. Chains of any length work the same way.
Sanity check the direction
A smaller unit always gives a bigger number. Converting metres to centimetres must increase the number; converting grams to kilograms must decrease it. Checking the direction catches an inverted conversion factor at once.
Step 2: Try It Yourself
Tap and try it out.
| Kilometres | Metres |
|---|---|
| 1 | 9 |
| 2 | 18 |
| 3 | 27 |
| 4 | 36 |
Every row is the same ratio. 1 to 9 is the same comparison as 5 to 45.
Hundreds of metres
Step 3: Watch an Example
One step at a time.
Watch Ana Convert Both Ways
Ana has 3 km and 4500 m, and wants both in metres.
- Step 1
Kilometres to metres is going smaller, so she multiplies: 3 × 1000 = 3000 m.
Step 4: Your Turn
Practice makes it stick.
The Bottle
Problem 1 of 2
2 litres is how many millilitres? (1 litre is 1000 ml.)
The Bag
Problem 2 of 2
3500 g is how many kilograms? (1 kg is 1000 g.)
Change the Unit
1 of 4
4 km in metres?
2 of 4
250 cm in metres? (100 cm in a metre.)
3 of 4
2 hours in minutes?
4 of 4
180 minutes in hours?
Step 5: Quick Check
Show what you know.
Question 1 of 1
5 km in metres?
What You Learned
- A unit conversion is a rate like any other.
- Going to a smaller unit multiplies; going to a bigger unit divides.
- The amount stays the same — only the unit changes.