Case 1
- Scale — the N in 1:N
- 25000
- Length measured on the model or map
- 4
100,000.00
Open with these valuesScale Calculator
100,000.00units
Result: 100,000.00 unitsA scale of 1:N means one unit on the model or map stands for N of the same units in reality, so the real length is the measured length times N. 4 cm on a 1:25000 map is 100000 cm — one kilometre. Going the other way, divide by N instead.
The numbers at a glance
Held fixed: Scale — the N in 1:N 25,000.
| Length measured on the model or map | Result |
|---|---|
| 1.000 | 25,000.00 |
| 2.000 | 50,000.00 |
| 3.000 | 75,000.00 |
| 4.000Your value | 100,000.00 |
| 5.000 | 125,000.00 |
| 6.000 | 150,000.00 |
| 7.000 | 175,000.00 |
| 8.000 | 200,000.00 |
Worked examples
Case 2
- Scale — the N in 1:N
- 87
- Length measured on the model or map
- 10
870.00
Open with these valuesCase 3
- Scale — the N in 1:N
- 160
- Length measured on the model or map
- 5
800.00
Open with these valuesHow it's calculated
Real length = measured × N
- StepEnter the N of your scale: 87 for HO trains, 25000 for a topographic map.
- StepMeasure the length on the model or map, in any unit you like.
- ResultRead the real length in that same unit, then convert it if you want.
Reference table
| Scale N, measured length | Scale | Real length |
|---|---|---|
| 1, 50 | 1:1, full size | 50 |
| 87, 10 | 1:87, HO gauge | 870 |
| 160, 5 | 1:160, N gauge | 800 |
| 25000, 1 | 1:25000, topographic map | 25000 |
| 25000, 4 | 1:25000, topographic map | 100000 |
| 100000, 2.5 | 1:100000, road map | 250000 |
Questions
How do I convert a measured length to the real-world length?
Multiply the length you measured on the model or map by the scale denominator N. For example, 4 cm on a 1:25000 map is 4 × 25000 = 100000 cm, which is 1 km. The answer is in the same unit you measured in.
What does a scale like 1:87 or 1:25000 mean?
One unit on the model or map represents N of the same units in the real world. So 1:87, the HO model railway scale, means 1 cm on the model is 87 cm in reality, and 1:25000 means 1 cm on the map is 250 m on the ground.
How do I work out the model size of a real object?
Divide instead of multiplying: model length = real length ÷ N. A 25 m real object at 1:160 becomes 25 ÷ 160 = 0.156 m, about 15.6 cm.
What are the common model and map scales?
Model railways use 1:87 for HO, 1:160 for N and 1:48 for O, while plastic kits often use 1:72, 1:48 or 1:24. Topographic maps commonly use 1:25000 or 1:50000. Enter whichever N your model or map states.
Is a scale the same as a ratio?
A scale is a ratio written as 1:N, with the model side fixed at 1. If yours is given as something like 4:100, divide both sides by the first number to reach the 1:N form — here 1:25 — before entering N.
Sources and last check
Information, not professional advice.