Floor Plan Scale
A floor plan scale connects the paper to the building: at 1:100, 1 cm on paper is 1 m in reality. You need it to measure a printed plan with a ruler, or to print your own plan so a builder can measure it. This guide explains the common metric and imperial scales, how to choose one, how to read lengths off a scaled plan, and how to print without losing the scale.
One room, two scales
What a scale means
A ratio scale such as 1:100 says one unit on paper stands for 100 of the same unit in reality, whatever the unit: 1 mm is 100 mm, 1 cm is 1 m. Imperial plans more often use a stated scale such as 1/4″ = 1′-0″, meaning a quarter inch on paper is a foot in the building. A quarter inch stands for twelve inches, so that scale is 1:48, close to but not the same as 1:50.
A scale bar is a ruler drawn on the sheet. Because it shrinks and grows with the paper, it stays right even when the plan has been copied or resized, which a written ratio does not.
Common floor plan scales
| 1 m on paper | 10 ft on paper | Commonly used for | |
|---|---|---|---|
| 1:20 | 50 mm | 152 mm (6 in) | Details such as a kitchen or bathroom wall |
| 1:50 | 20 mm | 61 mm (2.4 in) | Single rooms and furniture layouts |
| 1:100 | 10 mm | 30 mm (1.2 in) | A whole floor of a house or flat |
| 1:200 | 5 mm | 15 mm (0.6 in) | Large buildings and site layouts |
| 1/4″ = 1′-0″ (1:48) | 21 mm | 2.5 in | Imperial plans of homes |
| 1/8″ = 1′-0″ (1:96) | 10 mm | 1.25 in | Imperial plans of larger buildings |
Reading lengths from a scaled plan
Find the scale
It is in the title block or under the drawing, often with a scale bar.
Check the print
Measure the scale bar with a ruler. If it does not match its labels, the print was resized and only the scale bar can be trusted.
Measure and multiply
At 1:100, 37 mm on paper is 3.7 m. At 1/4″ = 1′-0″, every quarter inch is a foot.
Prefer written dimensions
A dimension written on the plan beats anything measured off the paper.
Worked example: choosing a scale for a sheet
The room in the drawing above is 4 × 3 m (13′1″ × 9′10″). At 1:50 it is 80 × 60 mm on paper; at 1:100 it is 40 × 30 mm. At 1/4″ = 1′-0″ the 13′1″ wall is about 3.3 in long.
Now a whole floor: a house 12 × 9 m (about 39′4″ × 29′6″) is 120 × 90 mm at 1:100, which fits an A4 or US Letter sheet with room for a title block. At 1:50 it is 240 × 180 mm, tight on A4 once margins are added, so A3 is the usual choice. A rough rule: pick the largest scale at which the whole floor fits the paper you can print, and use 1:50 for single rooms where furniture matters.
To work backwards, multiply: a wall that measures 37 mm on a 1:100 print is 3.7 m long.
Printing a plan to scale
A scale only holds if the drawing prints at 100%. Print dialogs often shrink pages to fit the margins, so turn off “fit to page” or “shrink to fit” and measure the scale bar afterwards.
The editor’s PDF export lets you choose 1:50, 1:100 or 1:200 on A0, A1, A2, A3, A4 or US Letter paper, in portrait or landscape, or fit the plan to the page and state the scale it used. Each sheet has a scale bar and a title block with the project name, date and units, and the dialog warns you if a floor does not fit the paper at the scale you chose.
Common scale mistakes
Treating 1/4″ as 1:50
It is 1:48. Over a 10 m wall the difference is about 40 cm.
Measuring a resized copy
A photocopy at 90% or a PDF opened at “fit” shifts every length. Use the scale bar.
Scaling off a screen
On screen only the proportions are true. Read written dimensions, or measure in the editor with M.
Too small a scale
At 1:200 a door is under 5 mm wide, too small to read furniture or swings.
When the scale matters
Plans for a builder or architect
They may measure off the drawing, so print at a stated scale and keep the scale bar.
Furniture cut-outs
At 1:50, paper cut-outs of your furniture can be moved around a printed plan.
Estate agent plans
Often marked “not to scale”: use their written room sizes, not a ruler.
Models
Pick the model scale first, then print the plan at the same scale as a base.
Frequently asked questions
What scale is a house floor plan usually drawn at?
Commonly 1:100 or 1:50 in metric and 1/4″ = 1′-0″ in imperial. Larger buildings use 1:200 or 1/8″ = 1′-0″.
What does 1:100 mean?
One unit on paper equals 100 of the same unit in reality: 1 cm is 1 m and 1 mm is 100 mm.
How do I turn 1/4 inch scale into a ratio?
A quarter inch stands for 12 inches, so it is 1:48. An eighth of an inch to the foot is 1:96.
How do I scale areas as well as lengths?
Convert each side to its real length first, then multiply. Areas scale by the square of the ratio: at 1:100, 1 cm² on paper is 1 m² in reality.
Do I choose a scale before drawing in the editor?
No. You draw at real size and choose the scale when you export a PDF. SVG exports are drawn at 1:100.