Printable PD ruler (free PDF)

A paper ruler you can print and cut out, accurate to the millimeter. Prefer not to print? Use the on-screen PD ruler, or let PDgo measure your PD automatically in 10 seconds.

Download the PDF ruler

A4 · one page · includes a bank-card scale check

How to use it

  1. Print at 100% scale. In the print dialog turn OFF "Fit to page" / "Shrink to fit". This is the step everyone gets wrong; a scaled print gives a wrong PD.
  2. Verify. Place any bank card in the dashed box on the printout. It must fit exactly. If not, re-print at 100%.
  3. Cut out the ruler along the top edge.
  4. Measure in a mirror: ruler flat against your brow, close your right eye, align 0 with your left pupil, then close your left eye and read the mark at your right pupil.
Skip the printer entirely. PDgo uses the iPhone's TrueDepth 3D camera: tap once, done in ~10 seconds, with per-eye values and a confidence rating. Get it on the App Store →