Free tool

PD ruler: measure your pupillary distance

PD is the distance between the centres of your pupils. Lens makers need it to centre your lenses.

Book a free eye test on WhatsApp Call 0325 2386838

PD ruler

Step 1. Set your screen size: hold a bank card or CNIC against the box and move the slider until the box is exactly as wide as the card

Step 2. This ruler is now true to size. Hold the screen flat against your forehead above a mirror, or ask someone to hold it under your eyes.

Step 3. Close your right eye and line up 0 with the centre of your left pupil. Without moving, open the right eye, close the left, and read the mark at the centre of the right pupil.

How to use it

Set the screen size with a bank card or CNIC.
Hold the ruler level, just below your eyes, in front of a mirror.
Line up zero with one pupil and read the other.
Repeat three times and take the middle value.

Your entries stay in your browser. Nothing is sent to us. The result is for information and is not a diagnosis.

Typical PD values

Most adults measure between 54 and 74 mm, and most children between 43 and 58 mm. Reading PD is about 3 mm less than distance PD.

Why PD matters

If the optical centres of the lenses do not sit in front of your pupils, strong lenses pull the eyes sideways and cause strain. The higher your number, the more exact the PD must be. For progressive lenses each eye is measured separately, along with the fitting height, in the frame you have chosen.

PD is measured as part of the free eye test at EyeBar Optical. If you order online, send your PD with your number.

Questions

Is PD written on my prescription?

Sometimes. If not, it can be measured in a minute at the shop.

Does PD change?

It grows in childhood and stays fixed in adults.

How accurate must PD be?

Within 1 to 2 mm for most lenses, and within 1 mm for high numbers and progressives.

Prepared by the team at Babar Homeopathic Clinic & EyeBar Optical, Kangan Pur. Last updated 3 October 2026. See our medical disclaimer.

Next steps

Free computerized eye testFrame size calculatorShop frames and lensesLens types

Free tools

More free eye tests and optical calculators

Free online eye testCheck how well each eye sees at distance in about three minutes. You need your phone or laptop, a card to set the screen size, and a few metres of space.Astigmatism testAstigmatism makes lines in one direction look sharper than lines in another. This dial shows it in under a minute.Colour blindness testRead the number hidden in each dotted plate. Six plates take about one minute.Amsler grid testThe Amsler grid checks the very centre of your vision. It takes one minute per eye.Reading glasses powerAfter 40 the eye's lens stiffens and near work gets harder. Enter your age to see the usual reading power.Glasses to contact lens powerA contact lens sits on the eye, so numbers above ±4.00 change. Enter your glasses number to see the contact lens power.

Visit us in Kot Bismillah, Kangan Pur

Address: Main Road, Kot Bismillah, Kangan Pur, Tehsil Chunian, District Kasur, Punjab
Open: 8:00 AM to 9:00 PM, every day
Phone: 0301 4117591
Phone and WhatsApp: 0325 2386838

Open in Google Maps Location and directions