Proper fitment is important!
Too tight will be distracting and painful, too loose will get you killed.
A proper fitting helmet will feel as comfortable as a knit winter hat, or a stretch-fit ball cap. Choose the loosest one that passes the tests (with the chin strap fastened):
1. Feels comfortable, with no pressure points pushing against your face , or anywhere for that matter. This includes the strap.
2. Shake your head vigorously (but not enough to hurt your neck) 'yes' and 'no', a small amount of movement of the helmet is okay, but use your better judgement and think about how the wind will affect it.
3. With the chin strap fastened, grab the lower rear of the helmet with both hands and try to pull it off, put some effort into this because the road will. It can move up your head a couple inches at most, but you must not be able to pull it off.

Remember to tell the sales person these rules, most of them don't know or care, they are only interested in selling right now.

Convertable to 3/4 with a face shield that can also be replaced with a visor, yes, a no fog mask 'cause I ride in the winter.

 

Rule #1: Buy a helmet designed for your shaped head. Some helmets are for round heads and some are for long-oval heads. If you don't get it right you'll never be comfortable.

After 40+ years of riding and going through several helmets, I prefer to buy them snug but not tight. After a little wear they loosen up. A too loose helmet isn't good.

 

The OP made excellent points and Captain Bligh above pointed out the biggest mistake that I think a lot of riders make, buying a helmet just because of the brand/color. Head shape generally falls into three shapes as pointed out in this article from Revzilla
https://www.revzilla.com/common-trea...e-helmet-guide

Helmet shell shapes will vary from one manufacture to the next with many of the larger companies offering some models that fit one shape and other models fitting another shape. If your head shape is a long oval and you decide on a helmet with a shell that is more of a round oval there is no way around the fact that you are going to have pressure spots on your forehead and really uncomfortable on long rides. Due to this the biggest mistake you can make is to choose a helmet based only on the manufacture, features or looks, the first thing you must do is make sure that model is going to fit your head shape

 

I ride with a Scorpion helmet, it has an air pump system in it, comfiest helmet I've ever used.

As someone above pointed out, the lining will give a bit on a new helmet so go for slightly too tight rather than just right on a new helmet

 

I have a mushroom head that often swells and turns a purple-ish color. It's been hard finding a helmet that fits.

 

My Choice....

 

Gee thanks for sharing that. Now go back to your room....

 

All good, However, I don't think a helmet will ever feel like a knit winter cap. Well not to me, especially since mine weighs over 4 pounds.

 

 

Ohhh! You're supposed to choose a helmet that fits your head? Who knew?

Thank you Fargo Helmet Expert!