How to measure from a photo

A photo can tell you real sizes, as long as you know one length in it and you measure things on the same flat surface. ScaleDraw makes it a two-minute job.

1. Take a straight-on photo

   Stand square to the wall or floor you want to measure, so it isn't skewed by perspective. Include something of known size on the same surface: a door, a tile, a tape measure or a sheet of A4 paper (297 × 210 mm).

2. Add it to the board

   Drag the photo onto the board, paste it, or use Menu → Import image….

3. Calibrate on the known object

   Press Calibrate, draw a line along the known object and type its real length.

4. Measure

   Use Measure to read off any distance on the same surface.

Limits worth knowing

• Only things on the same flat surface as your reference are measured correctly. Objects nearer or further away will be off.
• Wide-angle and phone lenses bend straight lines near the edges of the frame, so keep what you measure near the middle.