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Printable PD ruler

Measure your pupillary distance (the gap between the centres of your pupils) for glasses, with a printed ruler or a calibrated on-screen one.
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Short answer

Print the ruler at 100% scale and check it against a bank card (85.60 mm wide). Stand in front of a mirror, rest the ruler on your brow, close your right eye and line up 0 with the centre of your left pupil, then close your left eye and open your right: the mark under the centre of your right pupil is your PD in millimetres. Measure three times and use the middle value.

1. Print the ruler

In the print dialog choose “Actual size” or 100% (not “Fit to page”). Then lay a bank or ID card on the printed box: if it matches, the ruler is in true millimetres.

PD ruler (chadpsl.com). Print at 100% / Actual size. Check: a bank card fits the box exactly. Cut along the outline.
0102030405060708090100110120130140150millimetres · chadpsl.com
A bank card fits this box exactly

2. Measure

  1. Stand about 20 cm (8 in) from a mirror, in good light, looking straight ahead.
  2. Hold the ruler flat against your brow, level. In the mirror its numbers read backwards; that’s fine, count the marks.
  3. Close your right eye. Slide the ruler until 0 sits under the centre of your left pupil.
  4. Keep the ruler still. Close your left eye and open your right. Read the mark under the centre of your right pupil.
  5. Repeat three times and use the middle value. Or ask a friend at arm’s length to read it while you look past them into the distance.

That is your distance PD, used for most glasses. Reading glasses use a slightly smaller near PD: ask your optician for it.

No printer? Calibrate an on-screen ruler

Works best on a laptop or tablet: a card is wider than most phone screens.

  1. Hold any bank or ID card flat against your screen, over the box below.
  2. Drag the slider until the box is exactly as wide as the card.
  3. The ruler under it is then in real millimetres on this screen.

Not calibrated yet: the ruler below is only approximate.

0102030405060708090100millimetres · chadpsl.com

Choosing frames? See glasses for your face shape.

Questions people ask

What is a normal PD?

In a review of published measurements, the mean adult interpupillary distance was around 63 mm, and most adults fell between about 50 and 75 mm (Dodgson, 2004). Yours is simply yours: it isn’t better or worse anywhere in that range.

Is this accurate enough for glasses?

A careful home measurement is a useful check, but for prescription lenses use the PD your optician or optometrist measures, or ask them to check yours.

Does this tool see my face or send anything?

No. It is a ruler: it uses no camera, measures nothing itself and sends nothing anywhere. If you calibrate the on-screen ruler, that one number is kept in this browser only.

References

  1. Dodgson NA. Variation and extrema of human interpupillary distance. Proceedings of SPIE 5291, 2004. (Study)
  2. ISO/IEC ISO/IEC 7810, Identification cards: physical characteristics (the ID-1 card size, 85.60 × 53.98 mm, used by bank cards). International standard. (Standard)