Lenses, not just frames
How to Measure PD at Home
PD is the millimetres between pupils. Online glasses live or die on it. A millimetre or two is the difference between a clear centre and a headache.
Updated 27 Aug 2026 · 6 min read · how to measure PD at home
What PD is for
Lenses have an optical centre. That centre should sit in front of the pupil at the working distance the pair is built for. Distance PD is larger than near PD by a couple of millimetres. Progressives need distance PD plus a fitting height. A wrong PD decentres the lens and you buy ‘this pair is bad’ when the number was bad.
Adult distance PDs often sit around 54–68mm total. That range is not a default of 63.
A method that is good enough for mild single vision
Stand 40cm from a mirror, millimetre ruler against the brow, close the right eye, align 0 with the left pupil, open both, read the right pupil. Repeat three times. Average. A helper doing the same from the front is better. Marking dots on an old pair and measuring those is another shop trick.
- Mild single vision, cheap pair: home PD can suffice
- Progressives, high Rx, wrap: get it measured
- Dual PD if the site accepts it
When to stop DIY
If last year’s online pair swam, do not guess again. An optician PD takes a minute and is often free even if you buy elsewhere — ask. Fitting height for progressives is not a selfie. Spend the $0–$40 to measure rather than the $120 to reorder.
Questions, answered
- Is the PD on my old pair printed?
- Sometimes on the order receipt, almost never on the frame stamp. The stamp is lens width, bridge, temple.
- Single or dual PD?
- Dual if you can. Faces are not perfectly even. Online labs use it better when they have it.
- Can a wrong PD damage my eyes?
- It can give you strain and a pair you will not wear. Get a number that is real. That is a comfort issue, not a diagnosis.
