Scale Calculator
Convert a real measurement to a scale model or drawing size, convert back, or find the scale ratio from a real and a scaled measurement.
How scale works
A scale of 1:48 means 1 unit on the model or drawing stands for 48 of the same units in real life.
Scaled size = real size ÷ scale Real size = scaled size × scale
Worked example
A wall 20 ft long is 240 inches. At 1:48 (the common quarter-inch architectural scale), it is drawn 240 ÷ 48 = 5 inches long.
Common scales
| Scale | Typical use |
|---|---|
| 1:12 | Dollhouses (1 inch = 1 foot) |
| 1:24 and 1:25 | Model cars |
| 1:48 | Architectural drawings (¼ in = 1 ft) |
| 1:87 | HO model trains |
| 1:24,000 | Topographic maps |
Frequently asked questions
How do I find the scale factor?
Divide the scaled size by the real size, using the same units. 5 in ÷ 240 in = 1/48.
Do I need the same units?
Yes. Convert both measurements to the same unit before using a ratio scale.
How does scale affect area?
Areas scale by the square of the factor. At 1:10, an area is 100 times smaller.
What is 1/4 inch scale?
One quarter inch on the drawing equals one foot in reality, a ratio of 1:48.
Related calculators
- Percentage CalculatorPercent of a number, percent change and more.
- Fraction CalculatorAdd, subtract, multiply and divide fractions with steps.
- Area CalculatorArea of rectangles, circles, triangles and 5 more shapes.
- Diagonal CalculatorDiagonal of a rectangle, square or box.
- Factor CalculatorList all factors, factor pairs and the prime factorization.
- Average CalculatorMean, median, mode and range of any list of numbers.