The PD Journal
How to Read PD on Your Glasses Prescription (and What If It Is Missing)
Last updated: October 2026 | Reading time: 8 minutes
Short answer: PD is usually written as "PD" followed by a number in millimetres, such as PD 63, or as two numbers, such as 31.5/32. Many prescriptions do not include it at all, because PD is often measured when you order glasses, not at the eye exam. If yours is missing, you can ask the practice, have an optician measure it, or measure it yourself.
Where to look
Look near the bottom of the prescription or beside the lens columns. It may be labelled PD, DPD (distance), NPD (near), or IPD. A two-part value like 31/32 is monocular.
The rest of the prescription in plain words
| Abbreviation | Meaning |
|---|---|
| OD | Right eye (oculus dexter) |
| OS | Left eye (oculus sinister) |
| SPH | Spherical power: corrects short- or long-sightedness |
| CYL | Cylinder power: corrects astigmatism |
| AXIS | Direction of the astigmatism, 1–180 |
| ADD | Extra power for near vision in bifocals and progressives |
| PD | Distance between pupils, in mm |
| Prism / Base | Rarely: prism correction for eye alignment |
PD formats you may see
- 63: one binocular number.
- 63/60: distance PD and near PD, when two values are written separately and labelled DPD/NPD.
- 31.5/32: monocular right/left.
If it is not labelled, compare the size: values around 58 to 68 are usually binocular; values around 28 to 34 are monocular.
If your PD is missing
- Ask the practice. Many will tell you the PD they measured, even when it is not printed.
- Ask an optician. Many offer PD measurement for a small fee or free.
- Measure it yourself. Use our free PD tool with a bank card, or a ruler and mirror (how-to guide).
- Compare more than one reading. Two or three measurements that agree are more trustworthy than one.
For why practices often leave PD off, see why your optometrist won't give you your PD.
What to enter when ordering online
- Use your distance PD for normal single-vision glasses.
- Use near PD for reading-only glasses.
- Check whether the form wants one number or two.
More detail: buying glasses online: the PD guide.
A safety note
A self-measured PD is a good estimate, not a medical measurement. For progressive lenses, strong prescriptions, prisms, or children, have your PD and fitting measurements taken by a professional.
Related
What is pupillary distance? · Near PD vs distance PD · Binocular to monocular converter