Drawing scales
1" = 20' scale
1" = 20' is a 1:240 scale. An engineering scale used for residential site plans and plot plans. Conversion tables both ways.
Updated · FloorFigures
Short answer
1" = 20' means 1" on the drawing is 20' in real life: a ratio of 1:240. One inch on paper is 20 ft. An engineering scale used for residential site plans and plot plans.
1" = 20' conversion: inches on paper to feet
| On paper | Real size | In feet |
|---|---|---|
| 1/16" | 1'-3" | 1.25 ft |
| 1/8" | 2'-6" | 2.5 ft |
| 1/4" | 5'-0" | 5 ft |
| 1/2" | 10'-0" | 10 ft |
| 3/4" | 15'-0" | 15 ft |
| 1" | 20'-0" | 20 ft |
| 2" | 40'-0" | 40 ft |
| 3" | 60'-0" | 60 ft |
| 6" | 120'-0" | 120 ft |
| 12" | 240'-0" | 240 ft |
Feet to inches on paper at 1" = 20'
| Real size | On paper | Example |
|---|---|---|
| 1 ft | 1/16" | One foot |
| 3 ft | 1/8" | A standard door width |
| 10 ft | 1/2" | A small bedroom wall |
| 12 ft | 5/8" | A bedroom wall |
| 20 ft | 1" | A one-car garage depth |
| 36 ft | 1-13/16" | A small house's depth |
| 50 ft | 2-1/2" | A large house's width |
| 100 ft | 5" | A long lot line |
How much fits on a sheet
The largest area a full sheet can show at 1" = 20', before margins and title block:
| Sheet | Paper size | Real area shown |
|---|---|---|
| ARCH D | 36" × 24" | 720 × 480 ft |
| Tabloid (ANSI B) | 17" × 11" | 340 × 220 ft |
| Letter | 11" × 8.5" | 220 × 170 ft |
Is your plan really at 1" = 20'?
A scale note is only true at the paper size the drawing was made for. Print a 24" × 36" plan on letter paper with "fit to page", or export a PDF at a different page size, and every measurement shrinks by the same factor while the note still says 1" = 20'. Always check one printed dimension before you trust the scale.
FloorFigures does this for you on PDFs: it reads the printed dimensions, works out the real scale, and warns you when the note disagrees. It's free and runs in your browser.
Other engineering scales
| Scale | Ratio | Typical use |
|---|---|---|
| 1" = 10' | 1:120 | An engineering scale used for small site plans and detailed civil drawings. |
| 1" = 30' | 1:360 | An engineering scale used for larger lots and site plans. |
| 1" = 40' | 1:480 | An engineering scale used for subdivision and large site plans. |
| 1" = 50' | 1:600 | An engineering scale used for large sites and grading plans. |
| 1" = 100' | 1:1200 | An engineering scale used for area maps and large developments. |
Questions
- What does 1" = 20' scale mean?
- It means 1" on the drawing represents 20' in real life, a ratio of 1:240. One inch on the drawing is 20 ft in reality.
- How many feet is 1 inch at 1" = 20' scale?
- 1 inch on the drawing is 20 ft at 1" = 20', because the ratio is 1:240 and 240 inches is 20 feet.
- How do I convert 1" = 20' measurements to feet?
- Multiply the inches you measure on paper by 20 to get feet. For example, 3 inches on a 1" = 20' drawing is 60 ft.
- Is 1" = 20' the same as 1:240?
- Yes. 1" = 20' and 1:240 describe the same scale: real objects are 240 times larger than they're drawn.
- How do I check a plan is really at 1" = 20'?
- Measure a printed dimension. At 1" = 20', a 10-foot wall should measure 1/2" on paper. If it doesn't, the plan was resized (often by printing "fit to page") and you should set the scale from a dimension instead.