IPD stands for interpupillary distance—which simply means the distance between the center of your eyes. It’s important to know your IPD when it comes to VR and AR headsets because headsets can be adjusted to match your IPD for optimal image quality and comfort. Knowing your IPD is important for understanding which headsets are most suitable for your eyes. Luckily you can easily and automatically measure your IPD if you have a recent iPhone or iPad Pro, or use one of several simple measurement methods.

EyeMeasure is a free iOS app which uses the TrueDepth camera on recent iPhone and iPad Pro models to measure your IPD. Developer Dotty Digital claims the measurement is accurate within 0.5mm. Once you use the app the “far” IPD measurement is the one you’ll use when configuring your headset.

You can use the app to measure your IPD with the following iOS devices:

iPhone

  • iPhone 11 Pro Max
  • iPhone 11 Pro
  • iPhone 11
  • iPhone XS Max
  • iPhone XS
  • iPhone XR
  • iPhone X

If you don’t know which phone you have, learn how to identify your iPhone model.

iPad

  • iPad Pro 12.9-inch (4th generation)
  • iPad Pro 12.9-inch (3rd generation)
  • iPad Pro 11-inch (2nd generation)
  • iPad Pro 11-inch

If you don’t know which tablet you have, learn how to identify your iPad model.

Other Ways to Measure Your IPD

Image courtesy Will Folsom (CC BY 2.0)

If you don’t have access to one of the above devices for an automatic measurement, here’s other ways you can measure your IPD.

Ask Your Eye Doctor (most accurate)

The most accurate IPD measurement you’ll be able to get is from an eye-doctor. If you’ve been to one since you’ve reached your adult size, your doctor should have an accurate measurement on file; give them a call and ask if they can provide your IPD measurement in millimeters. If you’re younger than 20 and it’s been more than a year since you saw the eye-doctor, you may want to get a check-up to make sure you have an up-to-date measurement.

Online IPD Measure Tool (easiest)

You can measure your IPD with a browser-based tool like this one from Ace & Tate. This will work through your browser on your computer or smartphone. You’ll be asked to upload a photo of yourself holding any standard-sized magnetic strip card (ie: credit card or drivers license) which will be used to establish the correct scale for the measurement.

Use a Mirror (accurate but you need a ruler)

With a ruler and a mirror you can easily measure your IPD. Our friend Oliver Kreylos offers these simple instructions, along with a more detailed breakdown.

  1. Stand in front of a mirror and hold a ruler up to your nose, such that the measuring edge runs directly underneath both your pupils.
  2. Close your right eye and look directly at your left eye. Move the ruler such that the “0” mark appears directly underneath the center of your left pupil. Try to keep the ruler still for the next step.
  3. Close your left eye and look directly at your right eye. The mark directly underneath the center of your right pupil is your inter-pupillary distance.

Ask a Friend (but you need a ruler… and a friend)

Are you a vampire with no need for mirrors in your home? Ask a friend with a steady hand to hold a ruler directly under your eyes. Look straight forward at a distant object and ask your friend to align the “0” mark with the center of one pupil and then read the measurement under the center of your other pupil. That measurement is your IPD.

This is also an ideal way to measure the IPD of a VR novice to which you’re demoing VR.

Eyeball It (when you’re in a pinch)

This option may be the most error prone, but it’s probably better than nothing if you just need a quick and dirty alignment; it only works with headsets that have a physical IPD adjustment.

While inside the headset, close your non-dominant eye. With your dominant eye open, look at a sharp recognizable texture like text or the flat edge of an object. Begin adjusting the IPD setting back and forth to slowly find the position of maximum sharpness. This should get you in the ballpark of your ideal IPD setting. We would not recommend trying this exercise with both eyes open because it’s easier to misalign your IPD when using both eyes.

Thanks to Allan Hambrick who shared this method in the comments!

Why Correctly Setting Your IPD is Important in a VR or AR Headset

Image courtesy Dboybaker (CC BY 2.0)

Tricking our brains into believing we’re seeing another reality starts by feeding our eyes imagery which closely matches how we perceive the real world. That means making sure the images are correctly aligned with each eye, just like adjusting the width on a pair of binoculars.

Since we always see the real world from the perspective of or own IPD, correct alignment in a headset is important for matching our ingrained sense of 3D depth and scale. If the IPD of your headset is incorrectly set, the scale of the virtual world will appear to be slightly incorrect.

Even if a given headset doesn’t have a physical IPD adjustment, most headsets have a software IPD adjustment which can correct the sense of scale. In both cases you’ll need to know your own IPD measurement to set this properly.

Setting the correct IPD is also very important for maximizing image quality in VR and AR headsets.

Most headsets have lenses and displays which are designed to achieve maximum clarity and field of view when seen through the ‘optical center’ of the lens (this is also called the ‘sweet spot’). If the center of your eyes don’t align with the optical center of the lenses, you won’t get that maximum clarity and field of view; depending upon the lens, such misalignment can lead to a surprising reduction in visual quality.

Luckily, many headsets have physical IPD adjustments which allow you to change the distance between the lenses to align your eyes with the optical center of the lenses. All major headsets with physical IPD adjustments have digital readouts in millimeters that display inside the headset which you can use to match to your own IPD.

SEE ALSO
Everything We Know (Officially) About the FOV and IPD of Rift S & Quest

In summary, knowing your IPD and setting it correctly is important for achieving the best visual experience and comfort in any headset. And if your measured IPD is an outlier, you should make sure your headset of choice can accommodate your IPD; a headset with a physical IPD adjustment will support a much wider range of IPD measurements.

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  • sjefdeklerk

    That app measured 2 mm wrong

    • benz145

      What’s your known measurement based on?

      • sjefdeklerk

        Optometrist. But also confirmed via self measurement and what feels right in several headsets. Im 69 – 69.5 but the app claimed 71.5

        • benz145

          Thanks for the feedback, it would be great to get more feedback from people on accuracy.

  • Inter pupillary distance tends to be asymmetrical, like most human physiology, and can range from such a small offset it’s irrelevant, to a large offset that can prevent comfortable use especially for sessions of any length.

    Perhaps an important feature for future headsets is monocular IPD adjustment, for left/right offsets.

    Extending this concept further, vertical offset adjustment is also desirable; however designing lens adjustment in both axis is not simple.

    My left eye is slighty higher than my right (like many), in current headsets I have to slightly rotate the headset on my face to align this offset, its workable but not ideal.

    As display resolution increases and face gaskets improve to support longer sessions, adjustments to accommodate these common human asymmetries will become increasingly relevant; “content is king, but comfort is key!”

    https://uploads.disquscdn.com/images/d83f7ebc8f0db6f5d2bd7edfa89cf7af758399933b549e296a3f61af35100eb0.jpg

    • benz145

      All good points. In the not too distant future I hope that headsets start to incorporate automatic mechanical IPD adjustment based on eye-tracking measurements. As you say, asymmetric and multi-axis adjustability would be ideal.

      These issues may also be alleviated with improved lenses and advanced display technology light lightfields.

    • mirak

      They could have easily made it adjustable per eye, but they didn’t do it’

    • Heliosurge

      This is were Pimax has a good thing. They have added Left and Right offsets and height offsets in the software.

  • Allan Hambrick

    The best way with fixed axis IPD adjustable headsets is to simply close one eye and while looking straight ahead adjust ipd until image becomes as sharp as possible. That’s it, job done.

    • benz145

      This is a good quick and dirty option! Add this too the article, thanks for sharing : )

  • Zantetsu

    Not sure why, but my eyes don’t really care about the IPD setting. My optimal is 63.5 mm but I’ve had it at 67 accidentally and not even noticed. The difference across the entire IPD adjustment range is imperceptible to me.

    • dk

      there is always a curve to these things some percentage of people might not be affected that much and as always it depend on the type of movement in the game ….or the end result might be something small like on average getting tired slightly sooner then if it was at your ipd

    • Pablo C

      It used to be very important to me on my CV1, but after some months, now I can´t see a relevant difference among different IPD settings. I wonder if there is some brain adjustment on it.

  • You can also use binoculars to measure your IPD. Adjust the binoculars so that you can use them comfortably. Then use a ruler to measure the IPD. See the picture below.

    https://uploads.disquscdn.com/images/7cb949857c95d8632055cf79c9d11e8369dd79b3b1918c165f0c80bb7baf68b9.jpg

    • benz145

      I feel like this one will be highly error prone because the exit pupil on many binoculars will be plenty large for a wide variation of valid widths.

      • I just tried it with binoculars.
        Adjust the barrel distance, look through them for 10 seconds and adjust a little more until you’re comfortably looking around at the world. Set the binoculars down on a table and measure with a ruler. I got 69 mm while my real IPD is 70 mm according to a doctor’s measurement. So just 1mm off.
        Can you try, Ben?
        It’s explained in this video:
        https://youtu.be/aZ7_km8kTVg?t=52

        • benz145

          Cool, next time I have my binocs out I’ll give it a shot and see how close it is.

  • mirak

    “but you need a thousand dollars iphone”

    Seriously, who doesn’t have a ruler ??
    Or ca”t buy one for 2€

  • Pablo C

    I want to debate about IPD relevance.
    On my Rift CV1, I needed a strict IPD distance of 62 when I started to use it, but after a year using it daily, that changed. Now I pretty much don´t care about IPD adjustment, and I can´t see a relevant difference between different IPDs (even on setup). On my CV1, I can almost go all the way from start to end, without noticing a great deal. I recently got a Quest, and same thing, only the extreme IPD values are barely noticeable.
    So I wonder if there is some brain adjustment on this. May be a physical system for IPD adjustmen is not that important after getting used to.

  • piecutter2

    Go to your window. Raise the pane so that you can reach under it and press your nose and forehead against the glass to keep your head still. Now look at a far away, stationary object, preferably something that looks quite small and far away. While focusing on the object reach outside the glass with a fine tip felt marker and carefully touch the glass with the markers tip covering the object first on one eye with the opposite eye closed, then repeat for the other eye. When you have both eyes open the black dots on the glass should appear as one when you try to focus on the original object. Now measure the distance between the two dots on the glass. You now have your precise IPD.
    The smaller and further the object is, the more precise the measurement will be.

  • Very interesting guide, thanks for sharing it!

  • I like the Ace & Tate website, just send them a picture of your driver’s licence and/or credit card, along with your face.

    I wonder, if I include my Social Security Number could they tell if my identity was stolen?

  • Zaakie

    What the heck i have 75mm?

  • Andrey Lebedenko

    Selfie with the ruler + careful check of the picture on the big screen also works for IPD measurement.