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How To Measure Pupil Distance

The pupillary distance, or the PD as it is widely referred to, is an important measurement in creating accurate prescription glasses that won’t put even more strain on your eyes. This measurement is nothing more than the distance between your pupils, measured center to center, in millimeters.

Knowing this value will empower the technician from the laboratory where your eyeglasses are created, to craft them to perfectly fit your face. This fit would refer to aligning the center of the lens with your pupil, so that when you look through your glasses, your pupil will naturally overlap the center of the lens. This is why it's important to how to measure Pupil Distance.

This measurement is taken directly from you, without having anything to do with the frame you choose. Eye doctors or optical shop sellers may generally avoid to share this information with you, keeping it as something special for which you would have to pay extra. In reality, they could simply tell you this information.

If you’re being charged extra for this measurement, remember that you don’t really need to go through this. And that the doctor doesn’t have to measure your PD with your frame on. Since it’s simply a distance that applies to your pupils that we’re talking of, suffices to measure that distance with a ruler and do it correctly.

What’s more, as an adult, you can be sure that your PD will no longer change – as it happens to children and teenagers that continue to grow. For this reason, if you can remember the last measurement of your PD, you can use it for your new pair of glasses without hesitation.

Now that we’ve cleared that out, let us show you a few different ways in which you can find out what pupillary distance you have. Feel free to choose the one that works best for you to learn how to measure pupil distance:


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Let A Pro Handle The Measurement

This method will take a bit of extra time and money. You’ll have to call to an optical store from your neighborhood and schedule a consult. Ask the eye doctor or the optometrist for an eye exam and specifically inquire about your PD. The fee isn’t that much, but it is still money out of your pocket. If you don’t like the idea, consider the following options.


Ask Someone You Know To Take This Measurement For You, Using A MM Ruler

If you can involve someone you know, you can skip the visit to the doctor. Make sure you have a mm ruler – because the PD is measured in millimeters – and bring in the helper. You’ll ask that person to sit somewhere at an arm’s length away from you.

He’ll have to pick the ruler and place its 0 value straight on your left eye pupil middle. Keeping it as straight as possible, he should see what value will overlap the right eye pupil middle. The distance between these two points should be measured while you look straight ahead.

For accuracy, ask your helper to measure it more than once, just to make sure he got it right. As a side note, if you don’t have a mm ruler yourself, you can look up online for a printable ruler and use it instead.


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Do It All By Yourself, While Sitting In Front Of A Mirror, With A MM Ruler

The same process above-described, where a friend uses a mm ruler to measure your PD while standing in front of you, can be replicated even if you’re alone. You’ll need a mirror to look into, and that mirror will replace your helper.

Ideally, you should sit about 8 inches (20 cm) away from the mirror and keep an eye closed while you take the measurement. Say you’ll first close the right eye and keep the left one open. You should then place the ruler flat against the mirror and make sure it sits horizontally and with the mm scale up.

Align its zero mark with your left eye pupil center. Then switch it, by opening the right eye and closing the left one, all while keeping the ruler in place. Now you can read the value that sits on your right eye pupil center, which represents your PD. Again, feel free to repeat the process a few times until you can be sure you’ve measured it right.


Do It Yourself, Helped By A Friend, While Using A Non-Permanent Marker And A Ruler

This one is perhaps the easiest method, but only if you have a helping hand and a pair of functional eyeglasses. Simply put your eyeglasses on and ask the friend to stand in front of you. He’ll look you in the eye and use a non-permanent marker to make a dot on your lenses, right in the center of each pupil, while you’re looking at him straight ahead. Then, with a mm ruler, you can measure the distance between the two marked dots, and you have your PD.


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