Scale calculator
Choose the scale and type the real or the drawing measurement: the other shows up right away. Or enter both measurements to find the scale.
Real size and scale size
Find the scale
Available in: 
Scale calculator: what it is for
Choose the scale and type the real measurement or the one on the drawing, each with its own unit (mm, cm, m or km): the other is calculated right away. The tool also shows how much 1 cm on the drawing is in reality.
To find the scale of a plan or map, enter the real size of something known and its size on paper.
How to use
- Choose or type the scale.
- Type the real or drawing measurement.
- Use find the scale if you don't know it.
When to use it
- Read house and apartment floor plans.
- Measure distances on topographic maps.
- Build scale models and miniatures.
Frequently asked questions
What does a 1:100 scale mean?
That 1 unit on the drawing equals 100 real units: 1 cm on the plan is 100 cm (1 m) in reality. The bigger the number after the colon, the smaller the drawing.
Which scales are most used?
House and apartment floor plans usually use 1:50 or 1:100; site plans, 1:200 to 1:500; details, 1:20 or 1:10. Topographic maps use 1:24,000, 1:25,000, 1:50,000 and 1:100,000; scale model cars, 1:18, 1:24 and 1:43.
How do I find the scale of a drawing?
Measure on paper something of known size (an 80 cm door, for example) and use the find the scale option. If the door measures 1.6 cm on the drawing, the scale is 1:50.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.