# Scale Calculator

URL: https://speedycalculator.com/calculators/conversion/scale-conversion/
Last updated: 2026-10-25

> The scale calculator converts between real-world size and scaled size for maps, architectural drawings and scale models. Choose a common scale or enter your own ratio, then type either length.

## Inputs

- Scale
- Custom scale 1 :
- Real length (m, km, cm, mm, in, ft, yd)

## Results

- Scaled length

## Formula

```
scaled length = real length ÷ N   (for a 1:N scale)
```

## Explanation

A scale of 1:N means one unit on the drawing or model equals N of the same unit in reality. On a 1:50 drawing, 1 cm represents 50 cm; on an HO-scale (1:87) model railway, a 15 m locomotive is about 17 cm long.

### How to use the Scale Calculator

- **Scale**
- **Custom scale 1 :**
- **Real length**
- Every result field is editable: type into **Scaled length** and **Real length** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The real length is divided by N to give the scaled length. Type a scaled measurement into the result to get the real-world size.

### Inputs explained

FieldWhat to enterScaleChoose one: 1:12 (dollhouse), 1:24, 1:32, 1:48 (O scale, ¼″ = 1′) …Custom scale 1 :A numberReal lengthUnits: m, km, cm, mm, in, ft …

### Example values

How the main result changes when **Real length** changes and everything else stays at the example values above:

Real length (m)Scaled length (cm)7.58.610811.2512.91621517.221618.7521.52722.525.83243034.4432

## Worked example

Inputs — Scale: 1:87 (HO scale); Custom scale 1 :: 25; Real length: 15 m.

Results — **Scaled length = 17.2216 cm**.

## FAQ

**What does 1:100 mean?**
1 cm on the drawing is 100 cm (1 m) in reality.

**How long is a 6 ft person in 1:24 scale?**
3 inches.

**What is HO scale?**
1:87.1, the most popular model railway scale.

**What formula does the Scale Calculator use?**
scaled length = real length ÷ N   (for a 1:N scale).