Floor Plan Scale: 1/4" = 1'-0", 1:50 and Paper Sizes

A floor plan scale is the ratio between a length on paper and the real length it represents. The standard scale for US house plans is 1/4" = 1'-0", where a quarter inch on paper equals one foot of building (a ratio of 1:48); larger houses and site plans often use 1/8" = 1'-0" (1:96). Metric plans use round ratios such as 1:50 and 1:100. The right scale is the largest one at which the plan, its dimensions and its title block fit the sheet. Choosing it is step 2 of how to draw a floor plan.

Common floor plan scales

US architectural scales are written as "so many inches on paper = one foot". To turn one into a ratio, divide 12 by the paper inches: 12 ÷ ¼ = 48, so 1/4" = 1'-0" is 1:48.

Note that 1:50 is not the same as 1/4" = 1'-0", although they look alike: 1:48 is about 4% larger. A metric scale ruler read against an imperial plan, or the other way round, will be off by that much on every measurement. Canadian drawings meet this all the time; see metric vs imperial floor plans.

Paper sizes for floor plans

US drawings use two families of sheet sizes: ANSI sizes, which start from Letter, and ARCH sizes, used by architects. Outside North America, the ISO A series is the norm.

Many building departments now accept PDFs and set their own rules for the sheet size and scale they want; the permit drawing guide covers what reviewers usually ask for.

Will my plan fit? A worked example

Take FloorGen's 4-bed two-story template. Each floor is about 40½ × 28½ ft outside its walls, with 1,156.3 ft² per floor measured to the outside faces. At 1/4" = 1'-0", the walls alone take about 10⅛ × 7⅛ in of paper. That looks like it fits on 11 × 17 in, but the sheet also needs margins, dimension strings on all four sides, a title block and, in FloorGen's case, a room schedule.

Here is what FloorGen's print set picks for this house on each sheet, with the scale on Auto and the house drawn without a lot outline:

So for a house this size, 11 × 17 in is one step short of 1/4". The usual fixes are a larger sheet, splitting the floor into two sheets, or asking whether your department will accept 3/16" or 1/8". For a single room or a small ADU, 11 × 17 is usually plenty.

How FloorGen chooses a floor plan scale

In FloorGen, you draw at full size and choose the scale only when you print. Export → Print set makes one PDF with a sheet per floor, and its scale setting works like this:

• Paper: Letter, Tabloid (11 × 17 in), ARCH C, ARCH D, A4, A3, A2 or A1. A project set to the United States region starts on Tabloid.
• Auto tries the standard architectural scales from largest to smallest (1/2", 3/8", 1/4", 3/16", 1/8", 3/32" and 1/16" = 1'-0", then 1" = 20'-0" and 1/32" = 1'-0") and keeps the first at which the plan and its dimension strings fit the drawing area. It tries the sheet in portrait and landscape, with the room schedule beside or below the plan, and uses whichever gives the larger scale. Metric projects use 1:20, 1:25, 1:50, 1:75, 1:100 and so on.
• Fixed scales: 1/4", 1/8" or 1/16" = 1'-0" in feet and inches, or 1:50, 1:100 or 1:200 in metric. If the plan does not fit at the one you pick, the panel says so before you export, for example "First floor doesn't fit at 1/4" = 1'-0" on Tabloid, so it is printed at 3/16" = 1'-0"."
• Every sheet has a title block with the scale written in it, a four-segment graphic scale bar and a north arrow that follows the project's north angle.

The sheet is sized to everything drawn on that floor. If the project includes the lot outline, the first-floor sheet has to fit the whole lot, and the scale drops accordingly; delete the lot outline (or print from a copy without it) for a floor-plan-only sheet.

How to find the scale of a plan

If a plan has a written scale and a scale bar, check one against the other. If it has neither, or has been resized, find a dimension you trust (an overall dimension string, or a standard 36 in exterior door) and measure it on the paper:

A wall dimensioned 24'-0" measures 4.5 in on the printout.
24 ft x 12 in/ft = 288 in of building.
288 / 4.5 = 64, so the plan is at 1:64, which is 3/16" = 1'-0".

If the answer is not close to a standard scale, the sheet was probably resized to fit the paper, which is common with PDFs printed on "fit to page". Work from the written dimensions, not from the ruler. The same idea is how you scale a traced floor plan image in FloorGen: Set image scale asks you to click two points a known distance apart and type the real length.

Printing at the right scale

• Print PDFs at 100% / Actual size, never "fit to page", or the scale on the sheet will be wrong.
• After printing, measure the graphic scale bar with a ruler to confirm.
• Print on the sheet size the PDF was made for. A Tabloid PDF printed on Letter is at about 65% of its scale.
• If you send a plan to a print shop, tell them the sheet size and that it must be printed at full scale.

For more on reading the dimensions once the scale is right, see how to read a floor plan.