How to Measure Your PD at Home

Your pupillary distance (PD) is the measurement in millimetres between the centre of your pupils. It ensures your lenses are perfectly centred to your eyes — and getting it right makes all the difference to how clearly and comfortably you see.

Step-by-Step Guide

1

Gather what you need

You'll need a millimetre ruler, a mirror at eye level, and good lighting. A friend to help will make this easier and more accurate — but you can do it solo too.

2

Position yourself

Stand approximately 20cm (8 inches) from a mirror. Look only straight ahead — not up or down. Keep your gaze level and relaxed, as if looking at something in the distance.

3

Place and align the ruler

Hold the ruler flat against your brow, just above your eyes. Align the zero mark (0mm) with the centre of your left pupil. Keep the ruler as straight and level as possible.

4

Read the measurement

Without moving the ruler, read the millimetre mark that lines up with the centre of your right pupil. That number is your PD. Most adults measure between 54mm and 74mm. Repeat 2–3 times and take the average for best accuracy.

Your PD Measurement

Single PD

One number representing the total distance between both pupils. This is the most common format and works for most prescriptions.

58 - 74mm

Tips for Accuracy

  • Ask a friend to take the reading — it removes the temptation to look down at the ruler.
  • Always look straight ahead at a fixed point in the distance, not at your own reflection.
  • Use a ruler with clear millimetre markings — a standard school ruler works perfectly.
  • Good lighting is essential. Natural daylight or a bright room gives the clearest view of your pupils.

Common Questions

What if I can't get an exact number?

Rulers measure in whole millimetres, so simply read the nearest mark. A 1 mm difference has minimal impact on most prescriptions — use your most consistent reading.

Can I find my PD on my existing prescription?

Sometimes, yes. Look for a field labelled "PD", "P.D.", or "Inter-Pupillary Distance". Not all opticians include it automatically — if it's missing, you can ask them directly or measure it yourself using this guide.

Does my PD change over time?

Your PD is generally stable once you reach adulthood. It's unlikely to change significantly, so a measurement taken within the last few years is perfectly valid.