A scale tells you the ratio between a measurement on a drawing and the real-life measurement it represents. A scale of 1:100 means every 1 cm on the drawing = 100 cm (1 m) in real life.
Draw a rectangle 6 cm × 4 cm using a ruler. Label it "Scale 1:100".
Example 2 — Choose a suitable scale for a garden 15 m × 10 m to fit on A4 paper (max useful drawing area ≈ 24 cm × 18 cm).
Step 1
Try 1:100: \(15 \text{ m} \to 15 \text{ cm}\), \(10 \text{ m} \to 10 \text{ cm}\). Both fit on A4. ✓
Step 2
Try 1:50: \(15 \text{ m} \to 30 \text{ cm}\). Too wide for A4. ✗
Step 3
Best choice: 1:100 — fits comfortably and gives a clear drawing.
Rule of thumb: Choose the largest scale that still fits your paper. Larger scale = more detail, but must still fit. A 1:50 drawing is twice as detailed as 1:100.
✓ Quick Check 1 — Choosing and Applying Scales
Question 1 of 10
Drawing Accurately — Floor Plans and Measurements
Creating an accurate scale drawing requires care with measurement and technique. A ruler gives straight lines; a set square ensures right angles.
To draw to scale: Convert each real measurement → draw length (divide by scale factor)
To read from a scale drawing: Measure drawing length → real length (multiply by scale factor)
Example 3 — Draw a floor plan for a bedroom 4 m × 3 m at scale 1:50
Step 1
Convert: 4 m = 400 cm; \(400 \div 50 = 8 \text{ cm}\) on drawing.
Step 2
Convert: 3 m = 300 cm; \(300 \div 50 = 6 \text{ cm}\) on drawing.
Step 3
Using a ruler: draw a horizontal line 8 cm. Use a set square to draw a perpendicular 6 cm. Complete the rectangle.
Step 4
Label the drawing "Bedroom — Scale 1:50" and note real dimensions 4 m × 3 m.
Example 4 — On a 1:50 floor plan, a kitchen measures 7 cm × 5 cm. What are the real dimensions?
Real kitchen dimensions: \(\mathbf{3.5 \text{ m} \times 2.5 \text{ m}}\)
Common error: Forgetting to convert units before dividing. Always work in the same unit throughout. Convert metres to centimetres first, then apply the scale.
✓ Quick Check 2 — Drawing Accurately and Floor Plans
Question 1 of 10
Interpreting Scale Drawings — Maps and Real-Life Design
Reading scale drawings is just as important as creating them. Map scales, garden designs and architectural plans all require you to convert drawing distances to real distances.
Real area: \(7.5 \times 4 = \mathbf{30 \text{ m}^2}\)
Unit conversion for maps: 1:25 000 → 1 cm = 250 m = 0.25 km. A useful shortcut: divide the map distance (cm) by 4 to get km directly at scale 1:25 000.
Work out each answer, then type it in and click Check to see if you're right.
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Question
Your answer
Result
1
Scale 1:50. A room is 4 m long. How long is it on the drawing in cm?
2
Scale 1:100. A drawing shows 6 cm. What is the real length in metres?
3
Scale 1:200. A wall is 8 m long. How long is it on the plan in cm?
4
Scale 1:50. A drawing shows 10 cm. What is the real length in metres?
5
Scale 1:25. A door is 2 m tall. How tall is it on the drawing in cm?
6
Scale 1:100. A drawing shows 3.5 cm. What is the real length in metres?
7
Scale 1:50. A garden is 6 m wide. How wide is it on the plan in cm?
⚠ Things to Watch Out For
Choosing an unsuitable scale: The scale must make the drawing fit on the page and be large enough to be legible. If a room is 8 m × 5 m, 1:100 gives 8 cm × 5 cm — just right. 1:10 would be too large.
Not measuring drawn lengths accurately: Use a ruler carefully — 1 mm error on a 1:100 drawing represents 10 cm in real life.
Forgetting to label the scale: Always write the scale used (e.g. "Scale 1:50") on the drawing. Without this, the drawing is meaningless.
Converting real to drawing sizes: Real 6 m at 1:50 → 6 m = 600 cm → 600 ÷ 50 = 12 cm on drawing. Don't forget to work in consistent units.
North arrow on maps: When creating a map or site plan, always include a north arrow to indicate orientation.