01 / DRAWING
Scale converter
Convert a real-world length to its drawn length at a chosen scale.
GAD / FREE CALCULATOR
Drawing scale converter
A working calculator, a clear formula and examples you can check.
How it works
A drawing at 1:100 shows a real length one hundred times smaller. Enter the physical length in metres and the scale denominator; the result is the length to draw in millimetres. A 10 m wall becomes 100 mm at 1:100, 200 mm at 1:50 and 50 mm at 1:200.
Worked example
To read a printed drawing in the other direction, multiply measured millimetres by the denominator and divide by 1,000. A line measuring 25 mm on a 1:100 drawing represents 2.5 m. Check a known dimension first: a PDF printed with “fit to page” may no longer retain its stated scale.
Before using the result
Use the result for diagrams and early layout checks. CAD model space generally stores real dimensions; its drawing or viewport scale controls the printed representation. Changing units and changing scale are separate operations.
More useful references
Calculation stays in this browser. Inputs are not uploaded.
Questions to take into the work
How do I convert between real metres and drawing millimetres?
For scale 1:n, drawing millimetres = real metres × 1,000 ÷ n. A 10 m wall is 200 mm at 1:50 and 100 mm at 1:100. Reverse the operation to read a drawing: 25 mm at 1:100 represents 2.5 m. Use the denominator and units consistently.
Why can a printed PDF give the wrong scale measurement?
Printing with “fit to page” can resize the drawing. Check a labelled dimension or scale bar before measuring an unlabelled length. Changing the drawing’s scale is also different from changing model units: a CAD model generally retains real dimensions while its viewport controls the printed representation.
GAD Editorial · Answers reviewed 2026-10-18