Dual PD vs Single PD Calculator
Pupil to pupil, a single PD is just one number. Two numbers give a dual PD, one from the nose to each pupil. Our calculator converts one form of pupillary distance into the other.
What are the numbers for your right eye and your left eye?
A single eye typically measures from 28 to 36 mm.
What is your single PD?
Type both numbers to see your single PD.
Dual PD vs Single PD: The Difference
A single PD, which is also called binocular PD, gives the space between the centres of the two pupils, like 63 mm. The dual PD (also called monocular PD) records the distance from the middle of the nose out to each pupil, like 31/32 (Cleveland Clinic). First comes the right eye, then the left. Add both halves to find the single PD.
Which PD Should You Type?
When the order form shows two boxes and your record is a dual PD, fill in both values. With only a single PD, put that number in the box meant for one value. When you split the number in half, you are assuming the nose sits exactly at the midpoint, and it almost never does. A measured dual PD works better for strong prescriptions and progressive lenses.
How to Convert Dual PD to Single PD
Combine the two values: 31.5 + 32 = 63.5 mm. To reverse the process, take the single PD of 63 and divide by two, giving 31.5 per eye; this is only an estimate.
| PD | Each eye, even split | Near PD, estimate |
|---|---|---|
| 58 mm | 29 mm | 55 mm |
| 60 mm | 30 mm | 57 mm |
| 62 mm | 31 mm | 59 mm |
| 63 mm | 31.5 mm | 60 mm |
| 64 mm | 32 mm | 61 mm |
| 66 mm | 33 mm | 63 mm |
| 68 mm | 34 mm | 65 mm |
Questions About Dual and Single PD
Why does my PD show two numbers?
One possibility is a dual PD: a number for each eye, nearly the same. The other is a distance and near pair: two numbers about 3 mm apart, like 64/61.
Is PD different for each eye?
Yes. Symmetry in faces is unusual, so values such as 31/32 or 30.5/32.5 count as ordinary dual PDs.
What is the meaning of monocular and binocular PD?
Dual PD also goes by the name monocular PD: the distance from the middle of the nose to one pupil. A binocular PD is the same as a single PD, measured between the two pupils.