23 August 2026
By Tom Collins
tom@TheCork.ie
If you have ever bought glasses online, you may have encountered a surprisingly simple question: what is your pupillary distance (PD)?
PD is the distance, measured in millimetres, between the centres of your pupils. It is an important measurement when glasses are being made because the optical centres of the lenses need to be correctly positioned in front of your eyes.
Yet many customers are surprised to discover that their optician may be reluctant to give them their PD measurement.
That can leave consumers wondering: if the optician has measured it, why can’t they simply tell me what it is?
What is pupillary distance?
Your PD is used to position the optical centres of your spectacle lenses correctly.
It can be recorded as a single measurement—for example, 62 mm—or as separate measurements for each eye, such as 31 mm right and 31 mm left.
The individual measurements can be particularly useful because people’s faces are not necessarily perfectly symmetrical.
When you have an eye examination and subsequently order spectacles, your optician may measure your PD as part of the dispensing process.
So why might an optician not give it to you?
There is an important distinction between your spectacle prescription and measurements taken during the dispensing of spectacles.
Some opticians treat PD as part of the dispensing process rather than part of the eye-test prescription. As a result, a customer may receive a copy of their prescription containing their sphere, cylinder and axis measurements, but not their PD.
There is also an obvious commercial issue.
If an optician provides a customer with all the information needed to order glasses elsewhere, that customer can potentially take the information to another retailer—particularly an online glasses company.
That does not mean that every optician who does not volunteer a PD is deliberately trying to prevent online purchases. There can be legitimate professional reasons for the way measurements are taken and recorded.
Nevertheless, from a consumer’s perspective, the situation can feel unnecessarily opaque.
And there is a very simple way for consumers to check their own PD.
I tested an Android PD-measuring app
One interesting option is Pupil Distance PD Meter Pro, developed by vistech.projects.
The app uses the phone’s camera to estimate pupillary distance and is specifically designed for people who want to measure their PD before buying glasses, sunglasses or even a VR headset.
It is available through Google Play as a paid app. At the time of checking, Google Play showed it at $3.99, with more than 10,000 downloads and a rating of approximately 3.6 stars from around 390 reviews.
Pupil Distance PD Meter Pro on Google Play
The developer says the app includes a custom camera designed to improve measurement accuracy, measurements for near/reading PD, measurement history and a basic glasses try-on feature.
How does it work?
The principle is straightforward.
The app uses the phone’s camera and a known-size reference object—in this case, the user is guided through the process of positioning themselves and the phone correctly. The software can then calculate the distance between the pupils.
The crucial word is correctly.
The app is particularly sensitive to the position and orientation of the phone. The developer explicitly says that the phone needs to be held straight because this is important for accurate measurements.
That is also reflected in user reviews.
One reviewer complained that holding the phone completely straight while simultaneously taking the photograph was extremely awkward. The developer responded that the app has an automatic option that can take the photograph when the phone is correctly positioned.
Another reviewer in December 2025 had a similar complaint, saying that getting the phone into the required position was frustrating. Again, the developer explained that the automatic capture function could be enabled.
Does it actually work?
The reviews are mixed—but there are some impressive reports.
One reviewer reported using the app to measure their IPD for a Valve Index VR headset. They had previously been using a setting of approximately 68–70 mm but said the app measured their IPD at 62.5 mm. After changing the headset setting, they reported a dramatic improvement in clarity.
Other users, however, have reported inaccurate measurements or difficulty using the app.
Some older reviews specifically complain that the application produced measurements that differed substantially from measurements obtained by other methods.
That is an important warning.
A smartphone app should not automatically be assumed to be as accurate as a properly performed professional measurement.
The quality of the result depends on the camera, the positioning of the phone, lighting, the user’s position and, importantly, whether the instructions are followed precisely.
The biggest criticism: using it isn’t completely foolproof
The app’s biggest weakness appears to be usability rather than the basic concept.
Several reviews complain about the requirement to hold the phone in a particular orientation while also taking the photograph.
This is a genuine problem because a PD measurement is only useful if the photograph and calibration are correct.
The developer has attempted to address this with automatic image capture, which removes some of the difficulty.
So I would not describe this as an app that you simply open, point at your face and immediately get a guaranteed professional-grade measurement.
Instead, it is better regarded as a useful consumer measurement tool that requires care.
What I like about it
There are several things that make the app interesting.
It gives consumers another option.
If an optician won’t provide your PD, you are not necessarily left completely stuck.
It provides a numerical measurement.
Rather than guessing whether your PD is 61, 62 or 63 mm, you can use a dedicated measurement tool and obtain an actual figure.
It measures near/reading PD.
That is a useful feature because the distance involved when reading is different from looking into the distance. The app specifically advertises near/reading PD measurement.
It keeps measurement history.
That means you can retain previous measurements rather than having to start again every time.
It is inexpensive compared with the cost of a pair of glasses.
The current Google Play listing shows the app at $3.99.
What I don’t like
The main drawback is that accuracy cannot simply be taken for granted.
The Google Play reviews demonstrate both sides of the argument: some users report excellent results, while others report difficulty using the app or measurements they believe are inaccurate.
The app also has a relatively modest rating of around 3.6/5, which isn’t terrible, but it certainly isn’t evidence of universal reliability.
And because the app has not been updated since December 2024 according to the current Google Play listing, potential users should also be aware that it isn’t a particularly recently updated application.
My verdict
Pupil Distance PD Meter Pro is an interesting and potentially useful tool for consumers—but I would treat its result as a measurement to check, rather than unquestionable fact.
If you are buying inexpensive single-vision glasses online, obtaining a PD from an app may be perfectly useful as a starting point.
If the app gives you 62 mm, for example, and another independent measurement also gives you approximately 62 mm, confidence in the result increases.
If the app says 62 mm but an optician has previously measured you at 65 mm, I would investigate the discrepancy rather than simply choosing whichever number suits you.
For more expensive glasses, high prescriptions, multifocal/progressive lenses or situations where precise lens positioning is particularly important, professional measurement remains preferable.
But there is an important point here.
The existence of apps such as Pupil Distance PD Meter Pro demonstrates that PD is not some mysterious piece of information that consumers cannot understand or measure.
It is a numerical measurement.
And in an increasingly online marketplace for spectacles, consumers are understandably asking why they cannot simply be told what their own measurement is.
Your prescription and your PD are not the same thing
One reason for confusion is that people often assume their spectacle prescription contains everything required to manufacture their glasses.
It may not.
A prescription can contain measurements such as:
- Sphere (SPH)
- Cylinder (CYL)
- Axis
- Add, where applicable
- Prism, where applicable
PD is a separate measurement used when positioning the lenses.
Therefore, receiving a copy of your prescription does not necessarily mean you have received every measurement that an optician has taken during the dispensing process.
Should opticians simply tell customers their PD?
There is a strong consumer argument for transparency.
If an optician has measured a customer’s PD as part of providing an optical service, it is understandable that the customer would want to know the measurement—especially if they are asking for their own records or want to obtain spectacles elsewhere.
The issue becomes even more significant in an age when consumers routinely compare prices online.
A customer may pay for an eye examination, receive their prescription and then discover that an additional piece of information needed to order glasses has not been provided.
That can create the impression that the information is being withheld to keep the customer tied to the optician.
Whether that impression is justified in an individual case is another matter.
The bigger issue: consumer choice
Ultimately, the PD debate is about more than a number measured in millimetres.
It raises a wider question about consumer choice and access to information.
Consumers increasingly expect to be able to obtain copies of information relating to services they have paid for. They also expect to be able to compare prices and shop around.
Opticians, meanwhile, have professional responsibilities concerning the accurate measurement, fitting and dispensing of spectacles.
The sensible approach should therefore be one of transparency: customers should be able to understand what measurements have been taken, what information is contained in their prescription, and what additional measurements may be required when ordering glasses.
After all, your eyes belong to you—and knowing the measurements used to make your glasses should not feel like a closely guarded secret.