How to
How to Measure Your PD (Pupillary Distance) at Home
Short answer: your pupillary distance (PD) is the distance in millimetres between the centres of your two pupils. You can measure it at home in under a minute with a millimetre ruler and a mirror: line the ruler up across your brow, align the zero mark with the centre of your right pupil, and read the millimetre mark that sits over the centre of your left pupil. Most adults measure between about 50 and 70 mm, with an average near 63 mm.
Key takeaways
- PD is the distance between the centres of your pupils, measured in millimetres.
- It ensures each lens’s optical centre sits directly in front of your pupil, so your vision is clear and comfortable.
- The average adult PD is roughly 63 mm; most people fall between 50 and 70 mm.
- You can measure it with a ruler and mirror, with a friend, or with a digital tool.
- PD accuracy matters most for strong prescriptions and progressive lenses.
What is pupillary distance (PD)?
Pupillary distance is the horizontal distance, in millimetres, between the centres of your two pupils. It is one of the measurements an optician uses to fit your glasses, alongside your prescription. Its job is simple but important: it tells the lab exactly where to position the optical centre of each lens so that the clearest part of the lens sits right in front of each pupil.
Why does PD matter for your glasses?
Every lens has an optical centre — the point where it focuses most accurately and with the least distortion. When your PD is correct, those optical centres line up with your pupils and you look through the sweet spot of each lens. When your PD is off, you look through the lens slightly off-centre, which forces your eyes to compensate. The result can be eye strain, headaches, blurred vision or a pulling sensation, especially after a few hours of wear.
PD accuracy matters more as your prescription gets stronger, because a stronger lens bends light more, so an off-centre gaze has a bigger effect. It is especially critical for progressive lenses, where the corridor of clear vision is narrow and a wrong PD can make the lenses genuinely hard to use.
What is the average pupillary distance?
For most adults, PD falls between about 50 mm and 70 mm, with an average close to 63 mm (source: Cleveland Clinic, Pupillary Distance, retrieved 4 September 2026). On average it tends to be slightly larger for men than for women, though there is wide individual variation. Children have smaller PDs that change as they grow, which is one reason children’s glasses should always be measured rather than assumed. These are typical ranges, not rules — your own measurement is the only one that matters for your glasses.
How to measure your PD at home, step by step
You need a ruler marked in millimetres and a mirror. Work in good light and keep your head straight and level.
- Stand about 20 cm (8 inches) from a mirror, or face a friend.
- Hold the ruler flat against your brow, just above your eyes, with the millimetre scale facing the mirror.
- Look straight ahead at your own reflection and keep both eyes open.
- Align the ruler’s zero mark with the centre of your right pupil.
- Without moving the ruler or your head, read the millimetre mark that lines up with the centre of your left pupil. That number is your PD.
- Repeat two or three times and take the average. Measurements within 1–2 mm of each other are normal.
A useful trick: close your right eye and align the zero with your left pupil, then close your left eye and read the number over your right pupil. Switching eyes keeps your gaze steady and reduces error.
Measuring with a friend (more accurate)
It is easier and usually more accurate to have someone else measure for you, because you can look into the distance and keep your eyes relaxed. Sit slightly lower than your helper, look straight ahead at a fixed point across the room, and have them rest the ruler on the bridge of your nose and read pupil-centre to pupil-centre while you hold still.
Measuring your PD digitally
You can also measure PD with a digital tool that uses your device camera and a reference object for scale. This removes the parallax errors that make ruler measurements tricky to do alone. OpteLux’s VisionCraft Center includes a free face and PD measurement tool that does exactly this, so you can get a reliable number without a second person or a trip to a store.
Single PD, dual PD and near PD explained
You may be asked for different forms of PD. Here is what each means.
| Type | What it is | When it is used |
|---|---|---|
| Single (binocular) PD | One number for the total distance between both pupils | Most single-vision glasses |
| Dual (monocular) PD | Two numbers — each pupil to the centre of the nose bridge | Faces that are not perfectly symmetrical; progressives; high prescriptions |
| Distance PD | PD measured while looking at a far point | Standard for everyday distance glasses |
| Near PD | PD while focusing up close; usually about 3 mm smaller | Reading glasses |
If you only have a single PD but need dual, you can usually split it in half as an approximation, though a proper dual measurement is better for strong or progressive lenses.
Common mistakes when measuring PD
- Measuring pupil edge instead of centre. Always align to the centre of the pupil, not the inner or outer edge.
- Tilting your head. Keep your head level and your gaze straight ahead; a tilt skews the reading.
- Focusing on the ruler. Look into the distance or at your reflection, not at the ruler, or your eyes will converge and shrink the measurement.
- Using a worn or inch-only ruler. PD is always in millimetres; use a clear mm scale.
- Taking a single reading. Measure a few times and average.
How OpteLux makes this easy
Getting the PD right is the difference between glasses that feel effortless and glasses that quietly tire your eyes. Rather than rely on a shaky ruler measurement, the VisionCraft Center measures your PD and face dimensions from your device, then helps you choose frames that fit. Once you have your number, you can order any pair of OpteLux titanium eyeglasses with confidence that the lenses will be centred correctly for you.
Frequently asked questions
Can I measure my PD myself at home?
Yes. With a millimetre ruler and a mirror you can measure it in under a minute. Aligning the zero with one pupil and reading the number over the other. Measuring with a friend or a digital tool is usually more accurate.
What is the average PD for adults?
About 63 mm, with most adults falling between 50 and 70 mm. It is slightly larger on average for men than women, but individual variation is wide, so measure your own.
What happens if my PD is wrong on my glasses?
You look through the lens off-centre, which can cause eye strain, headaches, blurred vision or a pulling sensation. The stronger your prescription, the more a wrong PD is felt — and it matters most for progressive lenses.
Is PD the same for distance and reading glasses?
Not quite. Near PD, used for reading, is usually about 3 mm smaller than distance PD because your eyes converge slightly when focusing up close.
How accurate does my PD need to be?
Aim to be within about 1 mm. Small errors are tolerable for weak prescriptions but become noticeable with strong or progressive lenses, so it is worth measuring carefully or using a digital tool.
Is my PD on my glasses prescription?
Sometimes, but not always. In many places an optician is not required to include PD on a standard prescription, because it is a fitting measurement rather than part of the corrective prescription itself. If yours lists a number labelled “PD” — a single figure like 63, or two figures like 31.5 / 31.5 — you can use it directly. If it is missing, you are entitled to ask your optician for it, or simply measure it yourself using the steps above.
Do I need my PD to buy glasses online?
Yes. Without it, the lab has to default to an average that may not match you — and an off PD is one of the most common reasons online glasses feel “not quite right.” Providing an accurate PD is the single most useful thing you can do to make sure online glasses are comfortable from the first wear. It takes a minute to measure and pays off every day you wear them.
Measuring a child’s PD
Children’s PDs are smaller and change as they grow, so never reuse an old number or an adult average. The friend-measured method works best: have the child look at a fixed point across the room while you rest the ruler on their brow and read pupil-centre to pupil-centre. If they cannot hold still, a digital tool that captures a single photo is often easier. Re-measure whenever they get new glasses.
Can I use an app to measure my PD?
Yes. Camera-based tools use a reference object of known size — often a standard card — to calculate the scale and measure your PD, which removes much of the parallax error of measuring alone. The VisionCraft Center includes a free version.
How do I convert a single PD to a dual PD?
As a rough approximation, divide the single PD in half for each eye — a 63 mm single PD becomes about 31.5 mm per side. This assumes a symmetrical face; for strong or progressive lenses, a proper dual measurement is better.
The bottom line
Your PD is a small number with a big effect: it puts the clearest part of each lens exactly where your eyes need it. Measure it with a ruler and mirror, or more reliably with a friend or a digital tool, take the average of a few readings, and keep it on hand for every pair you buy. Get it right and your glasses will feel like they were made for you — because, optically, they were.
Skip the shaky ruler. Measure your PD free with the VisionCraft Center, then choose your OpteLux titanium frames knowing the lenses will be centred for you. New to OpteLux? Take 25% off your first order.