Want to clarrify the sizes of AoEs grid and hex reusable maps...

[samcifer]

Okay, so now I finally am getting access to lv. 2 spells and took Shatter with plans to get Fireball once I unlock lv. 3 spells. My question is to clarify how many spaces are covered in each size of AoE. These always assume I am choosing a specific square to be the center of the AoE. So here's how large an area is covered:

5' Radius = a 3x3 area is covered, say from a spell like Ice Knife's secondary explosion or a meteor shot by Melf's Minute Meteors.

10' Radius = a 5x5 area for spells like Shatter.

15' Radius (as a hat if as I don't think there are any circular AoE spells that cover a 15' radius area) = a 4x4 area.

20' Radius = a 9x9 area, like for Fireball.

[samcifer]

So am I right or wrong on this? Still searching for an answer here.

[Christian]

The official rules, such as they are, are on page 251 of the DMG. There are two entire paragraphs under the heading Areas of Effect in the Using Miniatures section, which can be summarized as:


The area of effect is centered at a grid intersection
If the area covers at least half of a square, that square is in the AOE.


That is the total guidance given--no corner cases discussed (heh), no sample diagrams. You're pretty much on your own to work out what that means for a particular spell area of effect. For your particular instances, the results are:



5' radius sphere includes four squares, a 2x2 box.
10' radius includes 12 squares, a 4x4 box excluding the corners.
15' radius includes 32 squares, a 6x6 box excluding the corners.
20' radius includes 52 squares, an 8x8 box excluding three squares in each corner.


Things like cones, cubes, and lines can fill varying collections of squares on the grid depending on how they're oriented from the point of origin.

[samcifer]

The official rules, such as they are, are on page 251 of the DMG. There are two entire paragraphs under the heading Areas of Effect in the Using Miniatures section, which can be summarized as:


The area of effect is centered at a grid intersection
If the area covers at least half of a square, that square is in the AOE.


That is the total guidance given--no corner cases discussed (heh), no sample diagrams. You're pretty much on your own to work out what that means for a particular spell area of effect. For your particular instances, the results are:



5' radius sphere includes four squares, a 2x2 box.
10' radius includes 12 squares, a 4x4 box excluding the corners.
15' radius includes 32 squares, a 6x6 box excluding the corners.
20' radius includes 52 squares, an 8x8 box excluding three squares in each corner.


Things like cones, cubes, and lines can fill varying collections of squares on the grid depending on how they're oriented from the point of origin.

Okay. Thanks for explaining it.

[JackPhoenix]

Also, Ice Knife doesn't have radius, per se. It's aimed at single target, but after hit, it explode and damage anything adjecent to the target. While the effect is similar, it means its AoE is larger than 5' radius, but you aren't free to aim it at any point in space, you *must* target a creature.

MMM is 5' radius spell, with standard 2x2 area, as noted by Christian

[samcifer]

Part of why I ask is because I finally unlocked access to lv. 2 spells and have been considering taking Shatter, but with the CON save, maybe Scorching Ry would be better. I have a +4 mod and +3 proficiency and since they can hit up to 3 creatures up to 120' away, maybe that would be better until I ca finally get Fireball in 2 more levels.

[Kuulvheysoon]

Xanathar’s Guide to Everything Actually has a couple of pages dedicated to just this question. AFB right now, but I know that it’s in there.