How to measure your PD
Pupillary distance (PD) is the distance measured in millimeters between the centers of the pupils of the eyes. This measurement is different from person to person and also depends on whether they are looking at near objects or far away. It helps to ensure that the lenses will be located in the optimum position. For progressive and bifocal lenses, this value is even more precise and it is split into two figures representing your left and right eye. This is known as monocular PD.
HOW TO MEASURE YOUR PD WITH A RULER METHOD 1
Stand facing a mirror that is positioned about 20 inches (50cm) away. Place the ruler on the bridge of your nose. Remember the start of the ruler (the zero scale) should be placed directly below the center of one eye's pupil.
Looking straight into the mirror, hold the ruler and mark the location on the ruler the center of the other eye's pupil.
Measure the distance in millimeters between the two marks. This is your PD.
Repeat the process two or three times for accuracy.
Record your results.
Remember you always need to keep your ruler steady and parallel to the floor using this method. If you have a friend to help, this will be much easier. You only need to stand still and let your friend do the measurement.
HOW TO MEASURE YOUR PD WITH A RULER METHOD 2
Here is another way to measure PD that some claim is very accurate, for your reference.
- Have a marker ready.
- Focus on a single object at least 20 feet (6 meters) away.
- Use your marker, on your right lens, precisely put a dot directly over the distant object.
- Repeat for your left eye.
- This is the important step. Now with both eyes open, the two dots should overlap into one single dot. If not, repeat steps 4 and 5 until you get one overlapped dot.
- Then, measure the distance between the two dots on your lenses with a ruler.
- That's your distance PD!
- If you need a near PD for reading or computer glasses, simply do the same but the object you choose is exactly the one you will be looking at, say, a newspaper, or a computer screen.
- The pupillary distance measurement is accurate with insignificant margins of error. Follow the above instructions to measure your own PD at home. Repeat these steps at least 3 times to get an accurate and consistent measurement. For instance, for powers higher than 2.75 Diopter, PD tolerance is usually less than or equal to 2.0 mm.
- You are highly encouraged to have an annual, comprehensive and dilated eye examination in order to receive precise prescription measurements, including your PD information. Simply send us your latest prescription when purchasing glasses online.