PD is the distance between your pupils (in millimeters). Getting it right aligns the optical center of your lenses for sharp, comfortable vision.
What is Pupillary Distance?
Pupillary Distance (PD) is the distance between the centers of your pupils. Lenses are made so their optical centers line up with your PD; that alignment is what gives you the clearest, most comfortable vision.
Before You Start (Setup Checklist)
- Stand in good, even lighting and face a mirror at eye level.
- Keep your head level and eyes relaxed—focus on something far away.
- Use a millimeter ruler (printable PD ruler works great).
- Remove bulky hats or hair that could tilt the ruler.
- Take 3–4 readings and use the most consistent value.
Why PD Matters
Accurate PD keeps your vision passing through each lens’s optical center. If PD is off, you may notice:
- Eye strain or fatigue
- Blurred or wavy vision
- Headaches—especially with screens
- Discomfort when reading or close work
Measure Your Own PD (Mirror Method)
Tools: millimeter ruler + mirror. Repeat 3–4 times for consistency.
- Stand about 8 inches (20 cm) from a mirror.
- Hold a millimeter ruler flat against your brow.
- Close your right eye. Align the ruler’s 0 mm with the center of your left pupil.
- Without moving the ruler, open your right eye and close your left.
- Read the mm mark centered on your right pupil. That number is your PD.
Tip: Keep your head still, look straight ahead, and don’t tilt the ruler.
Have a Friend Measure (Often Most Accurate)
- Keep both eyes open and look at a target 10–20 ft (3–6 m) away.
- Your friend places the ruler’s 0 mm over the center of one pupil.
- They measure straight across to the center of the other pupil.
- Have them sit/crouch slightly below your line of sight.
- Don’t track their hands—keep eyes on the far target.
- Record 3 readings; use the most consistent value.
Single vs Dual (Monocular) PD
| Type | What it is | Example | Best for |
|---|---|---|---|
| Single PD | Total distance from one pupil center to the other. | 62 mm |
Single-vision distance or general wear. |
| Dual (Monocular) PD | Distance from each pupil to the nose bridge (two numbers: right / left). |
32 / 30 mm (OD / OS) |
More precision; recommended for progressives and multifocals. |
Distance PD vs Near PD
Distance PD is used for everyday wear and driving. Near PD is used for reading and close work.
Subtract 3 mm from your distance PD.63 mm → 60 mm
Subtract 1.5 mm per eye from each monocular value.33/31 mm → 31.5/29.5 mm
If your prescription lists a Near PD, use that value as-is.
Which PD Do I Use?
- Single-vision distance / everyday: Distance PD (single or dual).
- Reading glasses: Near PD (single or dual).
- Progressives / multifocals: Dual (monocular) Distance PD is preferred.
- High prescriptions (±4.00 D or more): Dual PD gives better alignment.
Common Mistakes (and Quick Fixes)
- Looking at the ruler or friend: Focus on a far target so eyes don’t converge.
- Tilting the ruler: Keep it flat against your brow, not your nose.
- Uneven posture: Stand square to the mirror; level your head.
- Only one reading: Take multiple measurements and average/confirm the most consistent value.
Where to Find PD on a Prescription
Look for any of these notations:
- PD, P.D., IPD (interpupillary distance)
-
Dual/Monocular PD as two numbers, e.g.,
32/30(Right/Left) - Near PD for readers (may be listed separately)
Quick Reference
- Adults: 54–74 mm • Kids: 43–58 mm
- Measure 3–4× for consistency
- Use Distance PD for most everyday glasses
- Use Near PD for readers
- Millimeter ruler or printable PD ruler
- Mirror (solo method) or a friend (highest accuracy)
FAQs & Glossary
Is PD always on my prescription?
Do I need dual PD for progressives?
Why do repeated measurements differ slightly?
Glossary: OD / OS
Ready to Order?
Have your PD and prescription handy for a fast, accurate order.
