Does my eye doctor have to put my PD on my prescription?

Usually not under federal law. The Eyeglass Rule defines a prescription as the lens specifications from your exam plus whatever your state law requires (16 CFR 456.1(g)), and PD is not on the federal list. A few states require it; most do not. The FTC considered adding a federal PD requirement in its 2024 rule update and decided not to, though its business guidance encourages prescribers to hand over a PD they measured.

Can I get my PD anyway if they measured it?

Often yes. If the office measured your PD, that measurement is part of your patient record, and you generally have a right to copies of your records under federal health-records law and state records rules, though that request can take longer than the prescription itself. Asking politely at checkout works surprisingly often, and an optician fitting you for frames measures it as a matter of course.

How accurate does a home PD measurement need to be?

Within about a millimeter is the goal. Single-vision prescriptions at low to moderate power are forgiving; strong prescriptions, high astigmatism, and progressives are much less so, because lens optics are centered on your pupils and errors cause eye strain. For progressives or a strong prescription, get a professional measurement.

Most adults measure between about 54 and 74 millimeters, with the average in the low 60s. Some prescriptions list two numbers (like 31.5/32), which are per-eye distances from the bridge of your nose; online forms accept either format.

The classic gotcha

Pupillary distance: the one number your prescription is missing

Pupillary distance, or PD, is the distance between the centers of your pupils in millimeters. Every online glasses order asks for it, because the optical center of each lens has to sit directly in front of each pupil. And it is routinely absent from the prescription you just fought for. That is not an accident, and it is usually not illegal either. Here is the whole picture.

Why it is missing, legally

The Eyeglass Rule defines your prescription as the written lens specifications from your exam, plus anything your state law requires. (16 CFR 456.1(g)) PD is not on the federal list. The FTC looked hard at adding it during the rulemaking that produced the 2024 amendments and, in the end, did not. So unless your state is one of the few that requires PD on the prescription, the office can leave it off, and many do, knowing exactly which orders that blocks. The FTC's own compliance guidance encourages prescribers to hand over a measured PD and notes the patient is likely entitled to it through a records request anyway.

Two practical moves before you resort to measuring it yourself: ask at the visit ("could you add my PD to that?" works more often than you would think, especially asked before checkout), and check any past glasses order or old prescription, since PD changes very little in adulthood.

Measuring at home: the ground rules

You are aiming for the distance between pupil centers, in millimeters, to about a millimeter of accuracy. Use a millimeter ruler, work in good light, and take each measurement three times, keeping the value that repeats. Two cautions worth respecting: distance PD is slightly larger than reading PD (your eyes converge to read), so measure while focusing on something far away for regular glasses; and if your prescription is strong or progressive, a millimeter matters enough that a professional measurement is the right call.

Method one: mirror and ruler

Stand about 20 centimeters (8 inches) from a mirror, and hold a millimeter ruler flat against your brow, numbers facing the mirror.
Close your right eye. With your left eye open, line up the ruler's zero with the center of your left pupil.
Without moving the ruler or your head, close your left eye, open your right, and read the millimeter mark at the center of your right pupil. That reading is your PD.
Repeat three times. The eye-swap trick matters: it cancels the parallax error that comes from your viewing angle.

Method two: a friend and a ruler

Sit down and focus on a fixed point at least 3 meters (10 feet) behind your friend, over their shoulder. Keeping your focus at distance keeps your eyes from converging.
Your friend holds the ruler across your brow line, rests their hand against your forehead to steady it, and lines up zero with the center of one pupil.
They read the millimeter mark at the center of the other pupil, keeping their own head centered between your eyes to limit parallax.
Three passes; keep the number that repeats.

Method three: phone apps

Several eyewear retailers ship free PD measurement tools in their apps or on their sites, using your phone camera plus a reference object (usually a standard card held to your forehead) or the depth sensors on face-unlock phones. The depth-sensor versions are genuinely accurate; the card-reference versions are decent but sensitive to technique. A sensible workflow is to measure with an app, then confirm with the mirror method, and order once when the two agree within a millimeter.

Dual PD and reading glasses

Some measurements are written as two per-eye numbers, like 31.5/32, measured from the bridge of the nose to each pupil; faces are not symmetric, so the halves rarely match. Online forms accept single or dual PD. If you are ordering dedicated reading glasses, subtract about 3 millimeters from your distance PD (or use an app's near-PD mode), because your eyes turn inward at reading distance.

Common questions

Does my eye doctor have to put my PD on my prescription?: Usually not under federal law. The Eyeglass Rule defines a prescription as the lens specifications from your exam plus whatever your state law requires (16 CFR 456.1(g)), and PD is not on the federal list. A few states require it; most do not. The FTC considered adding a federal PD requirement in its 2024 rule update and decided not to, though its business guidance encourages prescribers to hand over a PD they measured.
Can I get my PD anyway if they measured it?: Often yes. If the office measured your PD, that measurement is part of your patient record, and you generally have a right to copies of your records under federal health-records law and state records rules, though that request can take longer than the prescription itself. Asking politely at checkout works surprisingly often, and an optician fitting you for frames measures it as a matter of course.
How accurate does a home PD measurement need to be?: Within about a millimeter is the goal. Single-vision prescriptions at low to moderate power are forgiving; strong prescriptions, high astigmatism, and progressives are much less so, because lens optics are centered on your pupils and errors cause eye strain. For progressives or a strong prescription, get a professional measurement.
What is a normal PD?: Most adults measure between about 54 and 74 millimeters, with the average in the low 60s. Some prescriptions list two numbers (like 31.5/32), which are per-eye distances from the bridge of your nose; online forms accept either format.

PD in hand, prescription in hand: the glasses buying guide compares where to spend them. If the office would not release the prescription itself, start with the script tool.