You can measure your pupillary distance (PD) at home in about five minutes with a millimetre ruler, a mirror and a friend (or your phone camera). Measure from the centre of one pupil to the centre of the other while looking at something in the distance, repeat it three times, and use the average. Most adults fall somewhere between roughly 54 and 74 mm.
This guide walks you through each method step by step, explains single vs dual PD, and shows how to avoid the most common measuring mistakes before you order prescription glasses online.
What is pupillary distance and why does it matter?
Pupillary distance is the distance, in millimetres, between the centres of your two pupils. Lens makers use it to place the optical centre of each lens directly in front of your eye.
When the optical centres line up with your pupils, you look through the part of the lens that matches your prescription most precisely. If they are noticeably off, many people find their new glasses feel "strange", especially with stronger prescriptions or progressive lenses.
PD is usually not printed on a standard prescription. If yours is missing, measuring it yourself is quick and easy. For help with the rest of your prescription, see our guide on how to read a prescription.
What you need
- A ruler with millimetre markings (a flat, rigid ruler works best)
- A mirror, or a friend to help you
- Good, even lighting
- A pen and paper to note your results
Method 1: Measure your PD with a mirror
- Stand about 20 cm (8 inches) from a mirror in a well-lit room.
- Hold the ruler flat against your brow, directly above your eyes. Keep your head straight.
- Close your right eye. Line up the 0 mm mark with the centre of your left pupil.
- Close your left eye and open your right eye. Read the millimetre mark that sits at the centre of your right pupil.
- Write the number down, then repeat the whole process two more times and use the average.
Tip: if you find it hard to see the centre of the pupil, line up with the edge of the iris on the same side for both eyes (left edge to left edge). The distance is the same.
Method 2: Ask a friend to measure
This is usually the most accurate home method, because you can keep both eyes on a distant point while someone else reads the ruler.
- Sit facing your friend at arm's length, at the same eye level.
- Look past their shoulder at an object at least 3 metres away. This keeps your eyes in the "distance" position.
- Your friend holds the ruler against your brow and lines up 0 mm with the centre of your right pupil (their left).
- They read the mark at the centre of your left pupil without moving the ruler.
- Repeat three times and average the result.
Your friend should close one eye while reading, to avoid parallax errors. For a printable step-by-step, visit our pupillary distance guide.
Method 3: Use a photo
If you are on your own and a mirror feels awkward, a photo can work as a backup:
- Hold a standard-size card (such as a loyalty or library card) flat under your nose, touching your face.
- Look straight at the camera from about 40 cm away and take a photo with your eyes open and relaxed.
- On a computer, measure the card width and the pupil-to-pupil distance in pixels. A standard card is 85.6 mm wide, so PD = pupil distance in pixels ÷ card width in pixels × 85.6.
This method is handy, but a small head tilt can change the result, so compare it with a mirror or friend measurement if you can.
Single PD vs dual PD
A single PD is one number for both eyes (for example 63). A dual PD, also called monocular PD, measures each eye separately from the centre of the bridge of your nose (for example 31.5/31.5 or 32/30). Faces are rarely perfectly symmetrical, so dual PD can be helpful.
| Type | Example | Best for |
|---|---|---|
| Single PD | 63 | Most single vision distance and reading lenses |
| Dual (monocular) PD | 32 / 31 | Progressive lenses, stronger prescriptions, asymmetrical faces |
| Near PD | Usually about 3 mm less than distance PD | Dedicated reading glasses |
To measure dual PD at home, ask your friend to measure from the centre of your nose bridge to the centre of each pupil separately while you look into the distance.
Common mistakes to avoid
- Looking at the ruler. Your eyes turn inwards when you focus close, which makes the number too small. Always look into the distance for distance PD.
- Tilting the ruler. Keep it horizontal and flat against your brow.
- Measuring once. Take three readings. If they differ by more than 1–2 mm, measure again.
- Confusing PD with frame size. PD is about your eyes; lens width and bridge are about the frame. Our frame size guide explains the difference.
Frequently asked questions
What is a normal PD?
For adults, PD is commonly between about 54 and 74 mm, with many people between 58 and 68 mm. Children usually have a smaller PD.
Is a home PD measurement accurate enough?
For most single vision lenses, a careful home measurement averaged over three readings works well for many people. For progressive lenses or high prescriptions, a dual PD from your optician is the most reliable option.
Can I use the PD from my old glasses?
Your PD belongs to your eyes, not your glasses. If an optician measured it before, that number is a good reference. Adult PD usually stays stable.
What if my prescription does not show PD?
That is very common. You can ask your optician for it, or measure it at home with one of the methods above and enter it in our lens selector.
Ready to order your new glasses?
Once you have your PD, choosing new frames is the fun part. Browse our prescription glasses, explore all eyeglasses, or check our best sellers. Not sure which shape to pick? Our frames and face shapes guide can help. Orders over €99 ship free, and every pair comes with our 14-day fit & style guarantee.
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