How exactly do I measure myself armpit to armpit?

You'll find the easiest (and most accurate) way to work out your armpit-to-armpit measurement is to simply measure a shirt or jacket that already fits you well.

Method A: Take a well-fitting shirt and use its measurements Method B (with 2nd person): Have someone take a tape measure and wrap it around your chest straight across and right under the armpits while your hands are at your sides. Divide this measurement in half Method C (alone): Take tape measure and wrap it around your chest as high as you can in the armpit area and as straight as you can across. Divide measurement by 2. If you want to be really precise, go to a tailor and ask them to take your measurements (even a neighborhood alterations tailor should be able to do this if they're competent, if you are super crazy about it you can go to a bespoke tailor and ask them to do it but expect to pay more for the service) for a small fee. PS: if you don't have an actual tape measure you could just use a string/cord/whatever thing of length and then measure that

This is hard to do on the body. Put your armpits on a table and measure them there.

Account for about 1/2 inch both sides due to armpit hair (depending on how much you manscape).

I would not recommend using string or cord. It can stretch during measurement which would skew the true measurement. Also, if using string to measure your chest, it can "sink" into your skin as you wrap it around your body, which would also give an inaccurate measurement. I saying all this from first hand experience.

The best thing to use is tailor's measuring tape which can be purchased just about anywhere for less than $1.00 I think every clothing geek should have one.

What do you guys do with the actual measurements? +2 inches? (does it matter if it's a blazer or a shirt/top/sweater?)

^^ I eat them. Measuring myself always makes me hungry.

srsly.

Use a measuring tape, stand up straight, inhale, take the tape around the widest part of your chest - that's your chest measurement. OR measure shirts/jackets you have that fit well in the chest - close up the front, have the material sit flat, and measure underarm to underarm. Just don't measure yourself pit to pit (whereas the widest part of your chest can be larger than around your underarms, a garment's chest is not bigger than its pit to pit - the pit to pit of a garment should be the widest part of the garment's chest). Your chest size is generally your suit size. +2" from that pit to pit is a slim fit chest. less tolerance than that can be tight and/or uncomfortable.

My experience is that inhaling will give you an inflated chest measurement (larger than it actually is).

How does one measure dick size? Deflated or fully inflated? And where does one begin? Is this something one needs help with from someone else? Or is it possible to get an accurate measurement on one's own?

And what does one then do with this information?

what happens when you buy clothes and can't breathe?

Ha ha.

when i'm measuring a suit pit to pit, so I measure from the very outside point while it's laying flat or do i measure from the seam of the pit (which is about an inch and a half in from the outside of the suit laying flat?)