Measure Your Pupillary Distance Online
Get your PD measurement online in just a few simple steps. Our free online tool helps you measure the distance between your pupils in millimetres, giving you the information needed when ordering prescription glasses.
There is no app to download. Simply use a phone, tablet or computer with a camera and follow the on-screen instructions.
[START FREE PD MEASUREMENT]
Quick • Easy to use • No app required
HOW TO MEASURE YOUR PD ONLINE
-
Start the measurement tool
Select “Start Free PD Measurement” and allow camera access when your browser asks for permission.
-
Position your face
Remove your glasses and look directly at the camera. Keep your head straight, your device at eye level and both eyes clearly visible.
-
Get your PD result
Follow the on-screen instructions. The tool will locate the centres of your pupils and display your pupillary distance in millimetres.
For the best result, measure your PD two or three times. If you receive noticeably different readings, improve the lighting, clean your camera lens and try again.
[MEASURE MY PD NOW]
WHAT IS PUPILLARY DISTANCE?
Pupillary distance, commonly shortened to PD, is the distance between the centres of your pupils. It is measured in millimetres and is one of the measurements used when making prescription glasses.
Your pupils are the dark circular openings in the centre of your eyes. Your PD helps the lens laboratory position the optical centre of each prescription lens correctly in front of your eyes.
Your pupillary distance may appear on your glasses prescription or dispensing record. However, because PD is a fitting measurement rather than part of your prescription strength, it may be recorded separately.
WHY IS AN ACCURATE PD MEASUREMENT IMPORTANT?
Every prescription lens has an optical centre—the area designed to sit directly in front of your pupil. An accurate PD measurement helps the laboratory align the optical centres of your lenses with your eyes.
If the lenses are not centred correctly, your vision may not feel as clear or comfortable as expected. Depending on your prescription and lens type, an incorrect measurement may contribute to eyestrain, headaches, visual distortion or general discomfort.
An accurate pupillary distance is particularly important when ordering:
• Strong prescription lenses
• Reading glasses
• Bifocal glasses
• Varifocal or progressive lenses
• Glasses with complex prescriptions
Your PD does not describe the strength of your prescription, and measuring it is not the same as having an eye examination.
SINGLE PD AND DUAL PD EXPLAINED
Your pupillary distance may be written as one number or two numbers.
Single PD
Single PD, also known as binocular PD, is the total distance from the centre of one pupil to the centre of the other pupil.
For example:
63 mm
Dual PD
Dual PD, also known as monocular PD, consists of two measurements. It measures the distance from the centre of the bridge of your nose to the centre of each pupil.
For example:
31/32 mm
The right-eye measurement is normally written first, followed by the left-eye measurement.
The two sides of a face are not always perfectly symmetrical, so your right and left PD values may be slightly different. Dual PD can help position each lens independently and may be requested for certain prescriptions or lens types.
DISTANCE PD AND NEAR PD
Distance PD is measured while you look at a faraway object. It is commonly used for distance glasses and many everyday single-vision prescriptions.
Near PD is measured while you focus on something close, such as a book or mobile phone. Your eyes turn slightly inward when looking at a nearby object, so your near PD is normally smaller than your distance PD.
Do not change or calculate your near PD unless your optician, eyewear retailer or prescription instructions specifically ask for it.
If you are ordering reading, bifocal, varifocal or progressive lenses, check which measurement is required. These lenses may need additional fitting information that a general online PD measurement tool cannot provide.
TIPS FOR AN ACCURATE ONLINE PD MEASUREMENT
Follow these recommendations to improve the accuracy and consistency of your result:
• Use a bright room with even lighting.
• Avoid standing with a bright window behind you.
• Remove your prescription glasses or sunglasses.
• Make sure your hair does not cover your eyes.
• Clean the front-facing camera lens.
• Hold your phone or computer camera at eye level.
• Face the camera directly.
• Do not tilt or turn your head.
• Keep a neutral expression.
• Look directly at the target shown on the screen.
• Follow any calibration-card instructions carefully.
• Repeat the measurement two or three times.
If the tool requires a bank-sized card for calibration, cover any private numbers and use only the side requested in the instructions.
WHAT IS AN AVERAGE PD?
Pupillary distance varies naturally from person to person. Many adults have a single PD somewhere within a broad range of approximately 50 to 70 mm.
Children normally have smaller PD measurements, and their pupillary distance can change as their face grows.
An average PD should never replace your own measurement. A value outside the typical range is not necessarily incorrect, but it is sensible to repeat the measurement and ask an optician to confirm it before ordering glasses.
OTHER WAYS TO MEASURE YOUR PD
Ask an optician
An optician can measure your pupillary distance using professional equipment such as a pupillometer. This is the preferred option when you need the highest level of confidence or require additional fitting measurements.
Use a ruler and mirror
You can manually measure your PD using a mirror and a ruler marked in millimetres.
Stand in a well-lit room and hold the ruler horizontally above or below your eyes. Align the zero mark with the centre of one pupil and read the millimetre mark that lines up with the centre of the other pupil.
Repeat the process several times without moving or tilting the ruler. Manual measurement can be difficult, so asking another person to help may produce a more consistent result.
Use a printable PD ruler
A correctly scaled printable PD ruler can also be used. Print it at 100% or “actual size” and check its scale against a physical ruler before taking your measurement.
Do not use a printout that has been automatically reduced or enlarged to fit the page.
WHEN SHOULD AN OPTICIAN MEASURE YOUR PD?
Ask an optician to measure or confirm your pupillary distance if:
• Your repeated measurements are noticeably different.
• You have an eye-alignment condition such as strabismus.
• You are ordering bifocal, trifocal, varifocal or progressive lenses.
• You have a strong or complex prescription.
• The glasses are for a child.
• You are unsure whether you need single PD, dual PD or near PD.
• Your online result appears unusually high or low.
An online PD measurement can be useful when ordering glasses, but it is not a substitute for an eye examination or professional eye-care advice.
SAVE YOUR PD RESULT
Would you like to keep your PD result for later?
Enter your email address and we will send your measurement directly to your inbox, making it easy to find when you are ready to order your glasses.
Email address:
[EMAIL ADDRESS FIELD]
[EMAIL MY PD RESULT]
Optional marketing consent:
☐ I would also like to receive eyewear offers, product news and helpful updates from Low Cost Glasses. I understand that I can unsubscribe at any time.
Receiving your PD result by email is separate from agreeing to receive marketing messages. Please read our Privacy Policy to learn how we handle your information.
FREQUENTLY ASKED QUESTIONS
Can I measure my PD online for free?
Yes. You can use our free online PD measurement tool on a compatible phone, tablet or computer with a camera. Follow the positioning instructions carefully and repeat the measurement to check that your result is consistent.
Do I need to download an app?
No. The PD measurement tool works through your web browser, so you do not need to install an application.
Can I measure my PD while wearing glasses?
Remove your glasses unless the tool specifically instructs you to keep them on. Frames, reflections and tinted lenses may prevent the camera from locating the centres of your pupils correctly.
Is PD included on my glasses prescription?
Sometimes, but not always. Pupillary distance is a fitting measurement rather than the strength of your prescription. Your optician may have recorded it separately when your previous glasses were dispensed.
Does pupillary distance change?
PD can change while a child is growing. It is generally more stable during adulthood, but using a recent and confirmed measurement is still recommended when ordering new glasses.
Is one PD number or two numbers better?
A single PD gives the total distance between your pupils. Dual PD provides separate measurements for the right and left eyes. Use the format requested by the prescription form or your dispensing professional.
Can I use distance PD for reading glasses?
Near PD is usually slightly smaller because your eyes turn inward when focusing on a nearby object. Check whether your order requires distance PD, near PD or another fitting measurement.
What should I do if I receive different results?
Check your lighting, camera position and head angle before measuring again. If the numbers continue to vary, do not guess or average widely different results. Ask an optician to take the measurement.
Is an online PD measurement an eye test?
No. The tool only measures the distance between your pupils. It does not check your eye health, diagnose conditions or provide a glasses prescription. You should continue to have regular eye examinations with a qualified eye-care professional.
READY TO CHOOSE YOUR NEW GLASSES?
Once you have measured and saved your pupillary distance, you can use the result when ordering your prescription glasses online.
Explore affordable prescription glasses for men and women at Low Cost Glasses, with a range of frame shapes, colours, sizes and lens options available.
[SHOP PRESCRIPTION GLASSES]
Important information: This online tool provides a pupillary distance estimate and is not an eye examination or medical service. For complex prescriptions, multifocal lenses, children, eye-alignment conditions or inconsistent results, ask a qualified optician to confirm the required measurements.