How to measure your pupillary distance (PD)
What is the pupillary distance (PD)?
The abbreviation PD stands for pupillary distance. Along with the sphere and other values, it is the key factor for a perfect fit of your glasses. The number indicating the pupillary distance is given in millimetres.
The usual PD range is 54–74 mm for adults and 43–53 mm for children. Some people have separate values for the right and left eye.
How do I find my PD?
Ideally you will find the PD in your glasses prescription. Since the PD value does not change in adulthood, an old prescription is sufficient.
It does not matter, however, whether you can find the PD value in your prescription or not. You can easily measure it yourself by following the few steps described below. All you need is a ruler (10 cm/4 inch is sufficient) and a mirror (or a friend).
Stand about 20 cm (8 inches) away from the mirror.
Hold the ruler horizontally against your eyebrows.
Close your right eye and align the zero point of the ruler with the center of your left pupil.
Open your right eye. Read the length (in mm) that you can see at the centre of your right pupil. This is your PD.
You can repeat the measurement several times (measure also from the right eye to the left eye). If you measure different lengths, use the average value.
With a friend
Stand in front of your friend so that you can still look straight ahead into the room.
Your friend should then hold the ruler to your eyebrows.
Close your right eye and look at something 3–5 m (10–16 ft) away.
Your friend aligns the zero of the ruler with the center of your left pupil.
Open your right eye and close your left. Your friend can then measure the length (in mm) to the centre of your right pupil.
Repeat the measurement several times (measure also from the right eye to the left). If you measure different lengths, please use the average value.
And that's it! Now you know your PD value – without seeing an ophthalmologist or optician.
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