Understanding the concept
Metric length units increase in powers of ten. A ruler commonly shows millimetres and centimetres, while room dimensions use metres and journeys use kilometres.
Before calculating, decide what the measurement describes, identify the starting units and choose a sensible level of precision.
Step-by-step method
To convert to a smaller metric unit, multiply; to a larger one, divide. Write the unit with every number.
- Write down the original measurement and its unit.
- Choose the formula or conversion factor appropriate to the task.
- Calculate carefully, keeping the units visible at each step.
- Check the answer against an estimate and the real-world situation.
Quick-reference table
Keep these facts handy when solving measurement questions.
| Measurement | Equivalent or interpretation |
|---|---|
| 10 mm | 1 cm |
| 100 cm | 1 m |
| 1,000 m | 1 km |
| 1 m | 1,000 mm |
Four worked examples
Each example shows the calculation and the units used.
Example 1: Table width
Example 2: Timber length
Example 3: Walk distance
Example 4: Short gap
Common mistakes
Check for these problems before finalising your answer.
- Confusing a 10-fold step (mm to cm) with a 100-fold step (cm to m).
- Dropping units from the answer.
- Rounding a measurement before a precision-sensitive task.
Practice questions
Try these without looking at the answers first.
Question 1. Convert 2.4 m to cm.
Show answer and explanation
240 cm; multiply by 100.
Question 2. Convert 360 mm to cm.
Show answer and explanation
36 cm; divide by 10.
Question 3. Convert 1,250 m to km.
Show answer and explanation
1.25 km; divide by 1,000.
Question 4. Convert 0.8 km to m.
Show answer and explanation
800 m; multiply by 1,000.
Question 5. Convert 95 cm to m.
Show answer and explanation
0.95 m; divide by 100.
Review checklist
- Can you name the unit and explain what is being measured?
- Can you choose the correct formula or conversion factor?
- Can you show your calculation and units clearly?
- Can you check whether the answer is realistic?