Architect vs engineer scales
Architect scales express a fraction of an inch per foot (¼″=1′-0″) and are used for building plans, sections and details. Engineer scales use one inch to a round number of feet (1″=20′) for site, civil and survey drawings. Metric scales (1:50, 1:100, 1:200, 1:500) are ratios used everywhere outside the US.
Architect scale reference (imperial)
| Architect scale | Ratio | Decimal factor |
|---|---|---|
| 3″ = 1′-0″ | 1:4 | 0.25 |
| 1½″ = 1′-0″ | 1:8 | 0.125 |
| 1″ = 1′-0″ | 1:12 | 0.08333 |
| ¾″ = 1′-0″ | 1:16 | 0.0625 |
| ½″ = 1′-0″ | 1:24 | 0.04167 |
| ⅜″ = 1′-0″ | 1:32 | 0.03125 |
| ¼″ = 1′-0″ | 1:48 | 0.02083 |
| ³⁄₁₆″ = 1′-0″ | 1:64 | 0.01563 |
| ⅛″ = 1′-0″ | 1:96 | 0.01042 |
| ³⁄₃₂″ = 1′-0″ | 1:128 | 0.00781 |
| ¹⁄₁₆″ = 1′-0″ | 1:192 | 0.00521 |
Engineer scale reference
| Engineer scale | Ratio | Decimal factor |
|---|---|---|
| 1″ = 10′ | 1:120 | 0.00833 |
| 1″ = 20′ | 1:240 | 0.00417 |
| 1″ = 30′ | 1:360 | 0.00278 |
| 1″ = 40′ | 1:480 | 0.00208 |
| 1″ = 50′ | 1:600 | 0.00167 |
| 1″ = 60′ | 1:720 | 0.00139 |
| 1″ = 100′ | 1:1200 | 0.00083 |
Metric architectural scales
Jump to a dedicated calculator: 1:20, 1:25, 1:50, 1:100, 1:200, 1:500, 1:1000.
Frequently asked questions
What is the difference between an architect and an engineer scale?
Architect scales use fractions of an inch to a foot (1/4"=1′, 1/8"=1′) for buildings and details. Engineer scales use one inch to a round number of feet (1"=20′, 1"=50′) for site plans, civil and survey work.
What is 1/4 inch scale as a ratio?
1/4"=1′ means a quarter inch represents 12 inches, so the ratio is 12 ÷ 0.25 = 1:48.
What are the common metric architectural scales?
The most common are 1:50 (rooms and details), 1:100 (whole floor plans), 1:200 and 1:500 (large buildings and site plans).