How to measure a PDF drawing
- Open the PDF. Choose Open your PDF in the tool above, or drop the file onto it. The drawing opens in this browser tab and is not sent anywhere, and files up to 300 MB work. No drawing to hand? The sample sheet is a floor plan to practise on.
- Calibrate the sheet. When your drawing opens, the Calibrate tool is already selected. Drag from one end of a dimension you trust to the other, such as a dimensioned wall, a grid spacing or the scale bar, and type its real length. If the PDF is still at its printed paper size, you can enter the drawing scale instead: choose Scale not set and pick a ratio from 1:1 to 1:2500, or an imperial scale such as ¼" = 1'-0".
- Check a second dimension. Measure another known length somewhere else on the sheet. If it reads wrong, the plot was resized or the first two points missed the dimension line. Calibrate again before you take anything off the drawing.
- Measure. Use Length for a single run and Polylength for a run with bends. For Area, click each corner of the room or zone, then click the first corner again, double-click or press Enter to finish; Perimeter works the same way for a boundary such as skirting or a slab edge. On a tablet, tap the corners and finish with a tap on the first corner, a double tap or the Finish button that appears beside the readout. Count puts a numbered mark on each fixture or symbol you click. Every figure is written on the drawing and listed under Markups, in the unit you calibrated in.
- Deduct and total. Draw a shaft or an opening as a second area inside the first, select both and choose Deduct opening, so the net figure shows the hole instead of a traced-around outline. Give each measurement a subject such as Flooring or Sockets; search the markups list for that subject and its total appears at the foot of the list.
Calibrate every page you measure
A scale belongs to the sheet it was set on. A drawing set often mixes scales, and a detail at 1:20 next to a plan at 1:100 reads five times too long if it borrows the plan’s scale. Calibrate on the longest dimension you can find, because the small error in placing two points matters less over a long distance than a short one. The guide to calibrating a PDF drawing goes through both ways of setting a scale and how to check one.
For a room with columns and shafts taken out, see measuring area on a PDF. For a full estimate, with waste and rates kept apart from the measured quantity, see quantity takeoff from a PDF.
What is free, and what needs an account
Opening your own drawings, calibrating, measuring, counting and deductions are free here, with nothing to sign up for. The work lasts as long as the tab: close it and the measurements are gone. To keep a drawing, or to take the figures away as a marked-up PDF, a print to scale or a CSV of quantities, you need an account. Redline Free exports a flattened PDF with a small Redline footer; a clean or editable PDF and printing come with Plus or Pro, and the CSV with Pro. Every account starts with 30 days of Pro, no card. The Revu 20 switch offer runs for accounts opened by 31 January 2027. Compare the plans.
Is my PDF uploaded?
No. Your browser reads the file on your own computer and keeps it, with your measurements, in the page’s memory. Neither is sent to Redline, and closing the tab clears both. Redline counts how often the tool is started each day, with no cookie and nothing that identifies you or the file.
How accurate are measurements on a PDF?
As accurate as the calibration and the points you place. On a PDF drawn from CAD, points snap to the drawing’s own line ends and corners; on a scan, zoom in before you click. Check a second known dimension after calibrating, and measure one room whose size you already know before you trust a total.
Can I measure a scanned drawing?
Yes, if the scan is square and not stretched. Calibrate it against a dimension on the scan itself rather than the scale printed in the title block, because scanning and resizing change the paper size.
Does it work on a Mac, an iPad or in Microsoft Edge?
Yes. It runs in current versions of Chrome, Edge, Safari and Firefox on Windows, macOS, Linux, iPad and Android tablets, with nothing to install. A mouse is quickest for a long takeoff; on a tablet, one finger or an Apple Pencil places points and two fingers zoom and move. Tap each corner of an area, then finish it by tapping its first corner again, double-tapping the last corner or pressing Finish on the bar that appears beside the readout. On a phone, open the tool full screen.
Can I save or export what I measured?
Not without an account. Here the drawing and its measurements last as long as the browser tab. With an account you can save the drawing, and Redline Free exports it as a flattened PDF with a small Redline footer. A clean or editable PDF and printing it to scale come with Plus or Pro, and a CSV of every quantity with Pro; every account has Pro for its first 30 days.