How to Measure Pupillary Distance (PD) at Home

What is PD?

PD is the distance between the centers of your pupils, measured in millimeters. A single PD gives one total number. A dual PD gives one number for each eye, measured from the center of the nose. Distance PD is measured while you look far away. Near PD is measured while you look at a close object.

Dual PD is not distance PD plus near PD. These labels answer different questions.

mmPD uses millimeters

1Single PD has one number

2Dual PD has two numbers

3×Repeat your reading

Read the label first

Two questions. Four common PD formats.

Single or dual tells you how the number is written. Distance or near tells you where you are looking. The two labels can appear together.

Single (binocular) PD

Dual (monocular) PD

The values are examples. Keep each dual value with its Right/OD or Left/OS label.

PD format	What it measures	Example	How it may appear
Single distance PD	Total distance between both pupils while looking far away	63 mm	PD 63
Dual distance PD	Nose center to each pupil while looking far away	31 / 32 mm	Right/OD and Left/OS values
Single near PD	Total distance between both pupils while looking at a close object	59 mm	Near PD 59
Dual near PD	Nose center to each pupil while looking at a close object	29 / 30 mm	Near Right and Near Left

Example numbers are for explanation only. Use your own measured or prescribed values.

Question 1How is PD written?

Single = one total number. Dual = one number for each eye.

Question 2Where are you looking?

Distance = far away. Near = a close object.

Choose a method

Use the most reliable option available.

A professional measurement gives the best accuracy. If you measure at home, use a calibrated ruler and compare 2–3 readings.

Best accuracy

Eye care professional

Best for progressive, bifocal, prism or strong prescriptions, children, or uneven results.

You need: An appointment
Main benefit: Professional tools and fitting checks

Mirror + printable ruler

A quick way to estimate one total distance PD at home.

You need: Mirror, bright light, calibrated ruler
Main limit: Head or ruler movement changes the result

Friend + millimeter ruler

A helper can make ruler alignment easier while you look at a far target.

You need: A helper and millimeter ruler
Main limit: Both people must keep still

Print. Check. Then measure.

Choose the PDF that matches your paper: A4 or US Letter.
Print at 100% or Actual Size.
Turn off Fit to Page.
Check the 50 mm line with a real ruler and the standard bank-card box.
If either check does not match, do not use the printout.

US Letter PDF A4 PDF

Mirror method

Measure one distance PD in 5 steps.

This method estimates a single, or binocular, distance PD. Keep the ruler level and repeat the full process.

Keep the ruler level and look straight at your reflection.

Set your position.

Stand about 8 in (20 cm) from a mirror in bright light. Remove your glasses and keep your head level.

Look straight ahead.

Look at your reflection. Keep your head still and your gaze straight.

Place the zero mark.

Close your right eye. Put 0 at the center of your left pupil and keep the ruler level.

Switch eyes.

Open your right eye and close your left. Do not move your head or the ruler.

Read and repeat.

Read the mark at the center of your right pupil. Repeat the full measurement 2–3 times.

Stop if the numbers keep changing. Check the print scale, ruler angle, light, head position, and gaze. If the readings still differ, ask an eye care professional.

Helper method

Ask a friend to measure.

Stand or sit at the same height in bright light.
Look at a point far behind your helper.
Keep your head straight while the helper holds the ruler level.
Align 0 with one pupil and read the mark at the other pupil.
Repeat 2–3 times. Record the result only when the readings agree.

Do not look at your helper or the ruler. Near gaze can change the reading.

Read your result

Match the number to its label.

Keep the original format. Do not split, swap, round, or convert a value to make it fit.

Example 1 · one numberPD 63

Single PD

One total measurement between both pupils.

Example 2 · two eye values31 / 32

Dual PD

One value for each eye. Keep Right/OD and Left/OS labels.

Example 3 · two viewing distances63 / 59

Distance / near

Far and close measurements. These are not right and left values.

Check	What to confirm
1. Unit	The value is in millimeters.
2. Format	You know whether it is single or dual.
3. Viewing distance	You know whether it is distance or near PD.
4. Eye labels	Each dual value stays with the correct eye.

Order at LAKOH

Enter the value without changing it.

Use Single PD (Binocular) for one total value. Choose I have two PD numbers (Dual / Monocular PD) only when the two values are labeled by eye.

If you have one value

PD formatSingle

Your record63.0 mm

Enter the one number exactly as measured.

If you have two values

1 · Right eye (OD)31.0 mm

2 · Left eye (OS)32.0 mm

Use the prescription order: Right (OD) first, then Left (OS). Never swap the values.

Your result	What to do
Single PD from 54–78 mm	Choose single PD and enter the one number.
Dual PD from 27–39 mm per eye	Choose two PD values and match each number to the correct eye.
Distance and near values are shown	Follow the lens instructions at checkout. Ask LAKOH if the field is unclear.
Your value is outside the available range	Do not round or change it. Contact LAKOH before ordering.

Two numbers do not always mean dual PD. A pair such as 63 / 60 may mean Distance PD / Near PD. Only use the dual fields when the values are labeled Right/OD and Left/OS.

Need help reading your numbers? Email contact@lakoh.com. Do not send sensitive health details that are not needed for your question.

Ordering progressive or bifocal lenses?

These lenses need more fitting information than a basic single-vision lens. A precise monocular distance PD may be needed, along with fitting height and other frame measurements.

Use professional measurements when available.
Do not divide a single PD in half to create dual PD.
Do not convert distance PD to near PD with a fixed subtraction.
Ask which measurements are required for the lens and frame you choose.

Accuracy check

Avoid these 8 mistakes.

×Mixing two label systems. Dual is not distance plus near.

×Scaling the PDF. Print at 100% and check the 50 mm line.

×Tilting the ruler. Keep it level across the face.

×Moving your head. Keep it straight and still.

×Looking at the helper. Look at a far target.

×Measuring once. Repeat the reading 2–3 times.

×Dividing by 2. That does not measure each eye.

×Using PD as frame size. PD centers lenses; it does not size frames.

When should a professional measure your PD?

Progressive, bifocal, prism, or high-power lenses
An order that needs fitting height
Repeated readings that differ
Eyes that are hard to align
A measurement for a child
Labels you do not understand

Frequently asked questions

PD questions, answered simply.

Is PD written on every glasses prescription?

Not always. A glasses prescription and a PD measurement are different records. Ask the provider who measured your eyes whether your PD is available.

Is dual PD the same as distance and near PD?

No. Dual PD gives a separate number for each eye. Distance and near PD describe where you are looking during the measurement.

Can I divide a single PD by 2 to get dual PD?

Dividing gives only an estimate. It does not measure each eye and can hide a natural left-right difference. Use a measured dual PD when separate values are required.

Why is near PD often smaller than distance PD?

The eyes turn inward when looking at a close object, so the pupil centers are often closer together. The difference is not the same for everyone. Do not use a fixed subtraction.

Which PD should I use for progressive glasses?

Use the measurements requested for the selected lens and frame. Progressive lenses may need precise monocular distance PD, fitting height, and other fitting details. Ask LAKOH or an eye care professional if the order form is unclear.

Can I use a phone app to measure PD?

Some apps estimate PD, but accuracy can vary with the device, camera position, light, and calibration. Compare an app result with a professional measurement or carefully repeated ruler readings.

Does PD tell me which frame size to buy?

No. PD helps position the optical center of the lenses. Frame size uses measurements such as lens width, bridge width, temple length, and total frame width.

What if my readings are different each time?

Check the print scale, light, head position, gaze, and ruler angle. Repeat the measurement. If the readings still differ, ask an eye care professional instead of guessing.

After you measure