Scale Calculator – Scale Drawing and Model Size
This scale calculator converts real-world lengths to scale lengths for drawings, blueprints, maps, models and miniatures, and back again. Pick a preset such as 1:12, 1:48 (quarter inch to the foot) or HO train scale 1:87, or type your own ratio. You can also find the scale itself by entering a real length and the length it is drawn at. Results show inches and fractions, feet, millimeters and centimeters at once, so you can read the tape measure or ruler you are using. It runs in your browser and works with US and metric units.
Scale Calculator
Convert real size to scale size, scale size to real size, or find the scale.
How to use the Scale Calculator
- Choose what you want: real to scale, scale to real, or find the scale.
- Pick a scale preset, or choose Custom and type the ratio.
- Enter the length and choose its unit.
- Read the converted length in inches, feet, millimeters and centimeters.
- Copy the result for your plan or model.
How scale works
A scale of 1:N means that one unit on the drawing stands for N units in real life. Real length divided by N gives the scale length, and scale length times N gives the real length. To find N, divide the real length by the length on the drawing.
Features
- Real to scale, scale to real, or find the scale
- Presets: architectural, model train, map and craft scales
- Results in inches with fractions, feet, mm and cm
- Custom ratio
- Works with US and metric units
- Copy and print
Frequently asked questions
What does a scale of 1:48 mean?
It means one unit on the drawing or model equals 48 of the same unit in real life. It is the same as a quarter inch to one foot, so a 10 foot wall is 2.5 inches long on the plan.
How do I convert a real length to scale?
Divide the real length by the scale number. A 20 foot room at 1:24 is 20 ÷ 24 = 0.833 feet, or 10 inches, on the drawing.
How do I find the scale of a drawing?
Divide the real length by the length shown on the drawing, both in the same unit. If a 15 foot wall is 7.5 inches on paper, 180 inches ÷ 7.5 inches gives a scale of 1:24.
What is HO scale?
HO model train scale is 1:87.1, so a real 40 foot boxcar is about 5.5 inches long as a model.
Can I mix feet and inches?
Pick the unit for your input and the results show every unit at once, including feet and inches with fractions to the nearest sixteenth.