How scale works
What does scale mean?
Scale is the ratio of a length in a drawing or model to the corresponding real length. Express both lengths in the same unit first. A scale of 1:50 means that one unit on the drawing represents 50 of the same units in reality.
Reading 1:50 and 1:100
At 1:50, 1 cm represents 50 cm. At 1:100, the same centimetre represents 100 cm, or 1 m. A larger denominator produces a smaller drawing of the same object. At 1:1 the lengths are equal; a positive n below 1 represents enlargement.
From reality to a drawing
Divide the real length by n. Example: 2.5 m = 250 cm; 250 ÷ 50 = 5 cm on a 1:50 drawing. Select Reality → drawing / model, enter 2.5 m, choose scale 50 and cm as the result unit.
From a drawing to reality
Multiply the drawing length by n. Example: 4 cm × 25 = 100 cm = 1 m. A 1 cm length at 1:50 represents 50 cm. Multiply the entered length, rather than treating the scale label itself as a dimension.
Changing units
1 m = 100 cm = 1000 mm, and 1 cm = 10 mm. Select input and output units independently. A real 1 m at 1:100 becomes 1 cm or 10 mm. Intermediate values are never rounded.
Understanding precision
Results use up to six decimal places. ≈ marks rounding: 1 mm at 1:3 gives ≈ 0.333333 mm. Display precision is not measurement accuracy: real accuracy depends on the input, measuring tool and line thickness.
Screens, scans and printing
The diagram is schematic. Browser zoom, resolution, DPI and system settings affect its physical size. Scans and photos may be distorted. Do not measure your screen with a ruler. When printing an external drawing, use 100% and verify a known reference dimension. Fit to page can change its scale. This tool does not produce scale-accurate printouts.
Common questions
Comma or decimal point? Both 2,5 and 2.5 work, without thousands separators. Is zero valid? As a dimension, yes; as a scale, no. Does this work for areas? No. Area ratios use the square of the scale and volume ratios use its cube. This calculator converts lengths only.
Practical limits
Use the calculator to plan models and understand dimensions. It does not replace approved construction drawings, tolerances or measurement checks. Follow labelled dimensions on an approved drawing rather than measuring a casually resized photograph.
Sources and verification
2026-10-31 · ARWIVO