Floor plan scale calculator

How the numbers are produced

Elm Cottage is the sheet that opens here. The drawing is 860 by 480 pixels at 10 pixels per millimetre, so a 400 pixel wall is 40 millimetres of paper. The reference runs from (100, 80) to (500, 80). A known length of 2.00 m makes that wall 1:50, because 40 mm times 50 is 2,000 mm. The living room is (100, 100), (500, 100), (500, 400), (100, 400): 400 by 300 pixels, 4.00 m by 3.00 m, and 3.00 m². The kitchen is (520, 100) to (760, 400): 240 by 300 pixels, 2.40 m by 3.00 m, and 1.80 m². The rooms sum to 4.80 m². Nine leaders are drawn: the reference plus four edges of each room. The living door from (180, 400) to (340, 400) is 160 pixels, which is 0.80 m. That door is a deduction, not a tenth leader.

Press 1:100 and the same 400 pixel reference becomes 4.00 m. Lengths double and areas multiply by four, so the living room is 12.00 m², the kitchen is 7.20 m², and the total is 19.20 m². Press 1/4 in = 1 ft and the ratio is 1:48, not 1:50. The reference reads 1.92 m, the living room 2.76 m², the kitchen 1.66 m², and the total 4.42 m². On 40 mm of paper, 1:48 is 1.92 m and 1:50 is 2.00 m, about 4 percent shorter. The 1:50 button returns the known-wall figures: 2.00 m and 4.80 m². Choosing a ratio clears the known-length segments and keeps the reference line, so the leader count stays at nine and the reference is remeasured.

A known wall replaces the scale with one segment. Type 4 in the known-length field, leave the ends at (100, 80) and (500, 80), and apply. The reference reads 4.00 m and the total reads 19.20 m², the same figures as 1:100. Adding a second line averages the two. The sample already has 400 pixels equal to 2.00 m. A second 400 pixel line entered as 3.00 m produces a mean of 0.00625 metres per pixel. The original reference then reads 2.50 m and the total reads 7.50 m². If either factor differs from the mean by more than 5 percent, the sheet says the lines do not agree and still uses the average. Clearing the scale keeps the 400 pixel line on the sheet and sets every real field to Not to scale. The warning says lengths and areas stay in drawing units only. The tool does not guess from a door, a bath, or a ceiling height.

The scale converter does not change the plan. It only converts a paper length, a real length, and a ratio. 100 mm at 1:100 is 10.00 m. 80 mm at 1:50 is 4.00 m. 35 mm at 1:100 is 3.50 m. 40 mm at 1:48 is 1.92 m. The other direction is always millimetres on paper: 10.00 m at 1:100 is 100.00 mm. If you know both the paper length and the real length, 100 mm and 10.00 m is the ratio 1:100. Paper can be millimetres, centimetres, or inches. Real lengths can be metres or feet. One foot is 0.3048 m. The converter rounds half away from zero to two decimal places, the same rule as the sheet.

Open a PDF, JPG, or PNG when you leave the sample. A PDF is rasterised at 2 pixels per PDF point, so a page of 430 by 240 points becomes 860 by 480 pixels and the Elm Cottage endpoints still match. Each PDF page keeps its own scale. Zoom steps by 100 percent from 100 percent to 400 percent inside a clipped frame. The view label reads 200 percent after one zoom-in. The measured pixels do not change. An empty file is refused with “This file is empty.” A text file is refused with “Use a PDF, JPG or PNG plan.” A renamed file whose bytes are not a real image is refused with “This file is not a readable PDF, JPG or PNG.” A truncated PDF is refused with “This PDF could not be opened.” A refused file leaves Elm Cottage in place, still 4.80 m². A file over 25 MB, or a drawing over 40 million pixels, is refused. HEIC, WebP, and DWG are not opened. Nothing is recognised by OCR.

Free downloads are floor-plan-measurements.png, floor-plan-measurements.pdf, floor-plan-measurements.csv, and floor-plan-measurements.dxf, plus floor-plan-project.json. Names stay generic. The free PDF is a text table, not the architectural sheet. The DXF is ASCII R12 with layers REFERENCE, ROOMS, and DOORS. There is no watermark and no account. The paid files are the auto-dimension PDF, the auto-dimension SVG, and a takeoff zip. The zip holds a schedule PDF with a signature page and a CSV. Every paid line prints its formula. There are no prices and no tin counts. The request that unlocks a paid file sends only the deliverable name and the format. The plan, the file name, the coordinates, and the measurements stay in this browser. Refreshing or closing the plan clears it. The empty state says the plan is not kept. Open the project file to bring Elm Cottage back at 3.00 m² and 4.80 m².

Where these figures get used

A homeowner with a 1:50 planning drawing can check the living room before ordering flooring. On this sample that room is 3.00 m², and 10 percent waste makes the floor line 3.30 m². The same person can switch the readout to feet: the 2.00 m wall is 6.56 ft and the 4.80 m² total is 51.67 ft², using 1 ft = 0.3048 m.

A student checking a 1:100 sheet can press that preset and read 4.00 m on the reference, 12.00 m² in the living room, and 19.20 m² overall. The squared scale factor is the reason the area grew by four while the wall only doubled. That arithmetic is also the subject of the floor plan dimensions page, which compares a manual 2.00 m label with an offset leader and lists 40 mm of paper at 1:20 through 1:192.

Someone tracing a second room uses the outline field. The pair 100,100 500,100 500,400 100,400 is a 400 by 300 pixel room. After the wall is calibrated to 2.00 m, that room is 3.00 m². Two corners are not enough: the sheet asks for at least 3 corners and leaves the living room at 3.00 m². An outline that crosses itself hides the area instead of inventing one.

Offset leaders, the 40 mm scale table, and the 1.92 m versus 2.00 m gap are drawn on the floor plan dimensions page.

Common questions

The rest of the desk

Each of these opens the same measuring rules on a different job. Calibration is shared. A scale you set on one page is not stored for the next visit.

• Measure floor plan
• Floor plan measurement tool
• Floor plan square footage calculator
• Room area calculator
• Floor plan takeoff