Knowing your IPD (“Inter Pupillary Distance” or “The distance between each eye”) can make a difference to your initial and subsequent experiences in Mixed Realty as without correct adjustment of the hardware/software to match your IPD one of your eyes will probably be looking at a sub optimal image the result of watt might have you walking away with a “meh” rather than a “wow!”
So how can I calculate my IPD?
Your optician can certainly tell you your IPD when you have your eyes checked but if you are not planning on doing that soon there are a number of Apps that will give you a pretty good figure:
More information: https://en.wikipedia.org/wiki/Pupillary_distance
NB All Mixed Reality headsets have adjustment for IPD but my understanding is that only the Samsung headset has a sensor to do this for you (this being a bit of a luxury for something that should be a “one off”?)
NB You should re-check your IPD every 5 years or so