Drawing scales
3" = 1'-0" scale
3" = 1'-0" is a 1:4 scale. Used for full-detail sections of trim, framing and connections. Conversion tables both ways.
Updated · FloorFigures
Short answer
3" = 1'-0" means 3" on the drawing is 1'-0" in real life: a ratio of 1:4. One inch on paper is 4". Used for full-detail sections of trim, framing and connections.
3" = 1'-0" conversion: inches on paper to feet
| On paper | Real size | In feet |
|---|---|---|
| 1/16" | 1/4" | 0.02 ft |
| 1/8" | 1/2" | 0.04 ft |
| 1/4" | 1" | 0.08 ft |
| 1/2" | 2" | 0.17 ft |
| 3/4" | 3" | 0.25 ft |
| 1" | 4" | 0.33 ft |
| 2" | 8" | 0.67 ft |
| 3" | 1'-0" | 1 ft |
| 6" | 2'-0" | 2 ft |
| 12" | 4'-0" | 4 ft |
Feet to inches on paper at 3" = 1'-0"
| Real size | On paper | Example |
|---|---|---|
| 1 ft | 3" | One foot |
| 3 ft | 9" | A standard door width |
| 10 ft | 30" | A small bedroom wall |
| 12 ft | 36" | A bedroom wall |
| 20 ft | 60" | A one-car garage depth |
| 36 ft | 108" | A small house's depth |
| 50 ft | 150" | A large house's width |
| 100 ft | 300" | A long lot line |
How much fits on a sheet
The largest area a full sheet can show at 3" = 1'-0", before margins and title block:
| Sheet | Paper size | Real area shown |
|---|---|---|
| ARCH D | 36" × 24" | 12 × 8 ft |
| Tabloid (ANSI B) | 17" × 11" | 6 × 4 ft |
| Letter | 11" × 8.5" | 4 × 3 ft |
Is your plan really at 3" = 1'-0"?
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 3" = 1'-0". 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 architectural scales
| Scale | Ratio | Typical use |
|---|---|---|
| 1/16" = 1'-0" | 1:192 | Used for overall plans of large buildings and small site plans. |
| 3/32" = 1'-0" | 1:128 | Used for floor plans of large buildings that won't fit at 1/8 inch. |
| 1/8" = 1'-0" | 1:96 | Used for floor plans of large homes and commercial buildings, and for key plans. |
| 3/16" = 1'-0" | 1:64 | Used for residential plans that are too big for the sheet at 1/4 inch. |
| 1/4" = 1'-0" | 1:48 | The standard scale for house floor plans and elevations in the US. |
| 3/8" = 1'-0" | 1:32 | Used for enlarged plans and interior elevations. |
| 1/2" = 1'-0" | 1:24 | Used for enlarged kitchen and bath plans and interior elevations. |
| 3/4" = 1'-0" | 1:16 | Used for cabinet elevations and construction details. |
| 1" = 1'-0" | 1:12 | Used for construction details. |
| 1-1/2" = 1'-0" | 1:8 | Used for large construction details such as stairs and millwork. |
Questions
- What does 3" = 1'-0" scale mean?
- It means 3" on the drawing represents 1'-0" in real life, a ratio of 1:4. One inch on the drawing is 4" in reality.
- How many feet is 1 inch at 3" = 1'-0" scale?
- 1 inch on the drawing is 4" at 3" = 1'-0", because the ratio is 1:4 and 4 inches is 0.33 feet.
- How do I convert 3" = 1'-0" measurements to feet?
- Multiply the inches you measure on paper by 0.333 to get feet. For example, 3 inches on a 3" = 1'-0" drawing is 1 ft.
- Is 3" = 1'-0" the same as 1:4?
- Yes. 3" = 1'-0" and 1:4 describe the same scale: real objects are 4 times larger than they're drawn.
- How do I check a plan is really at 3" = 1'-0"?
- Measure a printed dimension. At 3" = 1'-0", a 10-foot wall should measure 30" 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.