Self AoEs and Grids

[Cheesegear]

PHB, pg 192 says that ranges between two things are counted in square spaces.
DMG, pg 251 says that AoEs have corners as the Point of Origin. Which is fine when throwing ranged spells, however...

When a spell targets yourself as the target - as you take up the whole square - or uses yourself as the PoO, which is correct in 5e?

https://i1.wp.com/www.sageadvice.eu/wp-content/uploads/2016/03/centerx.jpg?fit=850%2C444&ssl=1

https://img.fireden.net/tg/image/1516/58/1516587332945.png

[Darc_Vader]

I’d say the second one, with the caveat that most self targeted aoes I can think of are worded something like “within 10 feet of you” (Arms of Hadar) or just “within range” (Sword Burst, Word of Radiance) (notice the lack of ‘radius’ in those). In contrast Fireball is “each creature in a 20 foot radius [of a point within range]”. Not to mention the idea of something like Sword Burst only hitting three enemies when you’re surrounded just feels incorrect to me.

[DrKerosene]

I think Chris Perkins answered this in a tweet.

Also, I believe your cones can be a bit longer diagonally. I’m under the impression that the simplified rules for distance make most “circles” into squares too, technically.

[PhoenixPhyre]

The DMG specifies that anything "more than half covered is affected". This is kind of a pain, though.

Xanathar's Guide includes an optional section for two other methods. The relevant one here is the Template method. Basically, do a 1":5' mapping and make a template the right size. Anything touched by the template is affected.

This means that a 5' self-targeted effect affects all adjacent squares but no further. A 10' self-targeted effect affects 2 in each direction except diagonally, where it only touches 1. Etc.

And cones are triangular: at any distance X, the width of the cone is X feet. A 15' cone is 15' wide at the furthest extent. So actual cones, not portions of a sphere with that radius.

And when it comes right down to it...don't worry about it all that much. 5e is designed to be able to be run in theater of the mind anyway, so things are never that precisely balanced.

[Merudo]

I've been using the chart included in the answer of this RPG stack exchange question (https://rpg.stackexchange.com/questions/19400/what-is-a-radius-on-a-square-grid).

The answer is for 3.5e though, so I don't know if it is RAW by 5e, or if alternate systems are possible.