Setting out
Drawing scale
- where
- real length (mm)
- drawing length (mm)
- scale denominator (1:n)
Explain this equation
Converts a length measured on a drawing into a real length, and back again, at a stated 1:n scale.
ld is the length on the paper in millimetres. n is the scale denominator: at 1:50, 1 mm on paper is 50 mm in real life. lr is the real length in millimetres. The calculator also gives lr in metres.
A 1:n scale shrinks everything by the same factor, so you multiply by n to go from drawing to real, and divide by n to go the other way.
40 mm on a 1:50 drawing is 2000 mm, or 2 m. At 1:100 the same 40 mm is 4 m. A 2 m wall on a 1:50 drawing should measure 40 mm.
Watch out: a written dimension always beats a scaled one. Photocopies, PDFs and screen zoom often change the true printed scale.
Convert a measured drawing length at a stated 1:n scale.
Enter your values to see the result.
Good to know
Prefer written dimensions. Check the print calibration; screen zoom and resized prints change the effective scale.
Sources
- Geometry / arithmetic
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.