TOOL

Pupillary distance calculator

Enter the PD you already have and this converts it into the numbers an optician's form asks for: left and right monocular PD, your near PD for reading glasses, and the same value in inches. It also tells you how your reading compares with published adult averages, so an obvious mistake stands out before you order.

Far PD

63.0 mm

Everyday distance glasses

Near PD

60.0 mm

Reading glasses

Per eye (est.)

31.5 mm

Right and left, if symmetrical

In inches

2.48 in

Far PD, 1 in = 25.4 mm

Reference values from the US Army ANSUR anthropometric survey of 3,976 adults as reported in Dodgson, "Variation and extrema of human interpupillary distance" (2004); the far-to-near difference from Gantz, Shneor & Doron, Journal of Optometry (2021). Nothing you type here leaves your browser.

What each number is for

Number	What it is	Which glasses need it
Far PD	Pupil centre to pupil centre with your eyes relaxed on something distant.	Everyday and distance glasses. This is the default an online form wants.
Near PD	The same distance measured while your eyes converge on something close — about 3 mm narrower.	Reading glasses, and the near zone of progressives.
Monocular PD	Bridge of the nose to each pupil, measured separately for left and right.	Progressives and strong prescriptions, where each lens has to be centred on its own eye.

A calculator can only convert a number you already have. If you still need the underlying measurement, the three ways to measure your PD at home cover a ruler and mirror, a friend with a ruler, and an iPhone reading it directly — and the Pupillary Distance app returns far, near and both monocular values in one pass.

Common questions

How do you calculate near PD from far PD?

Subtract about 3 mm. Your eyes converge slightly when you look at something close, so your near PD is a little narrower than your distance PD. Reading glasses use the near number; everyday distance glasses use the far one.

How do I split a single PD into two monocular PDs?

Halving your binocular PD gives an estimate — 63 mm becomes 31.5 mm per eye — and that is what this calculator does. Treat it as an approximation: most faces are not symmetrical. For progressive or high-power lenses, measure each eye separately rather than halving.

What counts as a normal pupillary distance?

Most adults fall between about 50 mm and 75 mm. A reading outside that range is unusual but not impossible; it more often means the measurement slipped than that your face is unusual.

Should I round my PD up or down?

Round to the nearest whole millimeter, and if you land exactly on a half, either neighbour is fine for single-vision lenses. Do not round a monocular PD by more than half a millimeter, and do not round at all if your optician asked for a decimal.

Is this calculator a substitute for measuring?

No. It converts and sanity-checks a number you already have; it cannot produce a PD from nothing. To get the underlying measurement, use a millimeter ruler and a mirror, ask someone to measure for you, or let an iPhone with a TrueDepth front camera read it directly.

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