Reading Architectural Scales

A drawing scale is just a ratio between what you measure on paper and the real-world size. US architectural scales are written as “inches per foot,” while metric drawings use a clean ratio.

US scales as ratios

“¼” = 1’-0"" means one foot of building is drawn as a quarter inch. As a pure ratio that’s 1:48 (because 12” ÷ ¼” = 48). The common scales:

• 1/8” = 1’-0” → 1:96
• 1/4” = 1’-0” → 1:48
• 1/2” = 1’-0” → 1:24
• 3/4” = 1’-0” → 1:16
• 1” = 1’-0” → 1:12

Metric ratios

Metric drawings skip the inches-per-foot step: 1:50 means one unit on paper is fifty units in reality. Typical plan scales are 1:50 and 1:100; details run 1:5 to 1:20; site plans 1:200 to 1:1000.

Converting

• Real → drawing: divide the real dimension by the ratio. At 1:48, a 24’ wall draws as 24 ÷ 48 = 0.5’ = 6” on paper.
• Drawing → real: multiply. A measured ½” at 1:48 is ½ × 48 = 24” = 2’.

The scale converter does this both directions across US and metric scales, so you can check a print or set up a sheet without doing the arithmetic by hand.