Does Pupillary Distance Have to Be Exact?

Pupillary distance – also known as interpupillary distance – is a measure of the distance between a subject’s pupils.

Finding Pupillary Distance

This measurement is factored into the creation of corrective lenses to help locate the optical center of the lenses. Millimeters are the measurement unit used as the industry standard.

Pupillary distance can be measured by machine – a “corneal reflex pupillometer” – or with a millimeter ruler by any optometrist or optical assistant. It can also be measured by you at home with a small ruler, if you’re careful. The pupillary distance measurement does not have to be 100% precise to be useful, as it can tolerate a fairly small error range. If you do measure your own pupillary distance, it is recommended that you try several attempts to be sure you get a fairly accurate measurement.

Measurement ranges

To give you an idea of the kind of measurement readings you should get, here are the typical ranges for various groups:

  • Average pupillary distance for an adult is between 54-68mm, with acceptable measurement deviations generally falling in between 48mm and 73mm.
  • The range for children is approximately 41-55mm.
  • The large majority (95 percentile) of adult males in the USA have a pupillary distance of 70mm while a small minority (5 percentile) measure 55mm.
  • The range for adult females in the USA is between 65mm and 53mm.
  • For Europeans the figures equate to roughly 1mm smaller than the above measurements.

How to Measure Pupillary Distance Yourself

If you recently had an eye exam and were given a written prescription, or have an older prescription on file, the prescription may already indicate your pupillary distance. If it does not, you’ll need to obtain that measurement. To do it yourself, follow these steps:

  1. Obtain a millimeter ruler and place it against your eyes, resting on the bridge of your nose.
  2. Line up the 0mm starting point with the outer side of either your left or right pupil.
  3. Look straight ahead and have someone else note the reading, or look directly into a mirror and note the reading yourself. (If using an assistant be sure they are at the same height as you when they record the measurement.)
  4. Once lined up correctly as stated in step 2, the millimeter mark that falls in the center of your opposite pupil is your pupillary distance.
  5. Repeat the process a few times to be sure you get the same result.
  1. Lisa says:

    If my PD is 53 (measured by my optometrist) but these glasses that I want online are for 54+ will that make a huge difference?

  2. Matt says:

    I had some old glasses that measured 32.5, but a remeasure put it at 27.5. Those new glasses made it difficult to see. My next ones also measured 27.5, but asked them to measure the very old ones and they got that 32.5, even though measuring my face, gets 27.5.

    Now I tell them to just ignore the measurement and just use 32.5. Unsure why it works, but it just does

  3. Michael says:

    JT from November 17th. Another piece of the puzzle you might want to check is the strength of the prescription. They put all kinds of corrective adjustments in my most recent pair of glasses, but none of them worked. I was ready to give up, Until I found an old pair of glasses I hadn’t used in a long time with a much lower prescription level. As far as I know there are no adjustments for astigmatism in this pair, but this pair seems to work the best. Still a bit of eye strain, but no double vision and see about 20/20. I plan to have them examined for prescription level and compare. Sometimes, it’s possible that the prescription could have been marked at the wrong strength. So, tell the optometrist/ophthalmologist to start like you never had a pair of glasses before. Your eyes may have improved or you may have gotten a bad eye exam in the past. So, eliminate the possibility that the glasses are too strong for you first.
    Also, I suggest to be careful in the eye exam to only say one slide is better if there is a noticeable difference otherwise say “no difference”. I think sometimes people try to see a difference when there isn’t a significant difference. In my case I think somebody did not enter the data in the computer right a time or two. The axis on my past couple of prescriptions has varied quite a lot, and none of these has worked yet. I guess that it isn’t as critical when the power of the lens is off? Who knows?

  4. JT says:

    I’m having the same issue as William. One Optician’s office machine measured me at 30.5 each eye. Then at a different office, a doctor measured me at 61mm with the ruler (ok that makes sense), but then the Optician’s machine (the one I hold up to my face like binoculars) measured me at R 30.5, L 29.5 (total of 60mm), and I believe their big machine, the one the intake person puts you on upon arrival where you sit down and put your face up to, measured me at 62mm.

    I am experiencing shadowing or ghosting around letters and numbers on TV, laptop, phone (and even signs in the distance are not completely clear) that is giving me eye strain which is giving me sometimes daily headaches. I’m now on my third doctor (1st Optometrist said he couldn’t fix it and suggested eye therapy, 2nd Ophthalmologist didn’t even do all the vertical/horizonal alignment tests and basically just blew off my concerns saying it’s Presbyopia, which while I may be at that age, I don’t believe it is what is causing this), and now 3rd Optometrist is measuring a different PD with his ruler than the Optician’s machine is, but we’re basing the new glasses PD on what the Optician’s machine measures. And actually, when I first went in, the Optometrist’s machine measured 3 different PD’s in a span of minutes, and the little light in the machine, the object I stare at, went out in one side during one of the measurements, so I question the accuracy of the machine, which is the PD they used for my glasses.

    I’ve been told my eyes are very sensitive to a prescription and have read if the PD is off, it can cause blurry vision and headaches, which is exactly what I am experiencing. I should also mention I have an Astigmatism which the latest Optometrist is saying is causing these shadow letter issues. I keep telling the eye doctors when I’m looking at the letters in the distance for the “what line can you read” test, that I can see the lowest line, but all the lines/letters, including the top biggest line, have shadows on them and are not clear, and they can’t do anything with their machines to make them clear. But because I can technically see the lines, they don’t see too concerned… BUT THIS IS A BIG ISSUE FOR ME THAT NO ONE SEEMS TO BE TAKING SERIOUSLY.

    I’ve basically been told glasses can’t fix the shadowing/ghosting issue, and now we’re trying contacts. I just got Biofinity Toric trial contact lenses yesterday, which supposedly are supposed to be better than glasses for a bad astigmatism, but they are immediately causing headaches due to warped vision (laptop screen looking like a trapezoid, when I stare down like at a counter top, the left side rises up, not the right though, so almost like a fishbowl effect but only in one corner, bottom left; and basically all letters and numbers are blurry, and can barely read my phone).

    I asked about keratoconus and was told if I had that it would have been discovered much earlier and younger (well, is it just possible doctors missed it or I got it later in life?). Also all three doctors said I do not have any eye diseases or medical conditions with the eyes (was dilated twice in a span of a month and a half), and I don’t have any other medical conditions, and don’t even take any prescriptions.

    So what is the best, most accurate way to measure the PD for a proper reading?

    Are there better machines, other than the ones eye dr.’s normally use, to gauge a better prescription to help with clarity of vision? To note, two different Dr’s in a span of two months measured me at different Axis’s (and one issue was the first Dr.’s office made my glasses with the wrong prescription, the wrong Axis, that I wore for 2 weeks… and both Dr. office’s measured those wrong glasses with different Axis’s on their Lensometers, again bringing into question the accuracy of these machines).

    How can two different Lensometers measure the Axis of actual glasses differently (also with the Lab not getting it correct when they made the glasses?)

    Are there specific tests for keratoconus?

    I know I have many questions, and appreciate any advice.

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