Scale Factor Calculator
Convert scale drawing measurements to real world sizes and vice versa. Calculate scale factor from any ratio format.
What do you want to calculate?
Scale ratio as 1:X, X:1, or fraction
Length on the scaled drawing
Actual length in real life
Unit for result
For engineering scales like 1" = 50'
First scale for comparison
Second scale for comparison
What does a scale ratio like 1:100 mean?
A 1:100 scale means 1 unit on the drawing equals 100 units in real life. A 1:100 floor plan - 1 cm on paper = 100 cm (1 meter) in reality. Similarly, a 1:1 scale is full size, and 100:1 is 100× larger than real (for small objects).
How do I convert scale to real measurement?
Multiply the scale drawing measurement by the scale factor. For 1:100, scale factor is 100. A 5 cm line on a 1:100 drawing = 5 × 100 = 500 cm = 5 m in real life. Always check if your scale ruler is in the same units first.
What is the difference between 1:50 and 1:100 scales?
1:50 is a LARGER scale than 1:100 (1:50 shows more detail). At 1:50, 1 cm = 50 cm real. At 1:100, 1 cm = 100 cm real. 1:50 draws things twice as big as 1:100 for the same real object. Architectural drawings commonly use 1:50, 1:100, 1:200.
What are common scale ratios used in architecture and engineering?
Architecture: 1:500 (site plan), 1:100 (floor plan), 1:50 (detail), 1:20 (large detail). Engineering: 1:1 (full size), 1:5, 1:20, 1:50. Maps: 1:2400 (US survey), 1:10000, 1:50000. Hobby: 1:144 (plastic model cars), 1:72 (planes), 1:35 (military models).