# On a grid, what is the area of effect of the Spirit Guardians spell?

I'm unclear on what the area of effect of Spirit Guardians is on a grid.

The spell has a range of "Self (15-foot radius)".

Additionally, the description of the Spirit Guardians spell says:

You call forth spirits to protect you. They flit around you to a distance of 15 feet for the duration.

The problem here is that on a grid, an "area of effect with a 15-foot radius" is not the same as a "all targets within a distance of 15 feet".

An area of effect with a 15-foot radius would fall under the general rules for areas of effect on a grid (DMG p. 251), for example as discuss here.

The later could be interpreted as a range of 15 feet, or 3 squares away on a 5 feet grid.

On a 5-foot grid, what does the area look like?

Does it take one of the following shapes?

This is not a duplicate of the question "When playing on a grid, how many Medium creatures fit inside the area of a Scroll of Protection's barrier during combat?"; the Scroll clearly has a cylinder area of effect, while the Spirit Guardians spell affects targets 15 feet away from the caster.

• Commented Mar 2, 2020 at 17:22
• Commented Mar 3, 2020 at 3:54
• Commented Mar 3, 2020 at 3:55
• Everyone, please remember to keep the comments focused on suggesting improvements to the question or asking for clarification, not for tangential discussions. Commented Mar 3, 2020 at 4:10
• Commented Mar 5, 2023 at 3:19

From the DMG pg. 251:

Choose an intersection of squares or hexes as the point of origin of an area of effect, then follow its rules as normal. If an area of effect is circular and covers at least half a square, it affects that square.

Under these rules, the area of effect of a spell originating from the center of a square would resemble the fourth example you've given.

That said, if you find yourself lacking a graphing calculator, at the time of play or are simply looking for a quick, effective solution, the groups I've played in have found success using the optional diagonal range rule from the DMG pg. 252 for determining distance along diagonals, which reads as follows.

When measuring range or moving diagonally on a grid, the first diagonal square counts as 5 feet, but the second diagonal square counts as 10 feet.

This pattern is repeated in the same way for each following diagonal step.

While this is most often applied to movement, it also works well for determining the radius of a spell, as, in general, it's a fairly decent approximation of the Pythagorean Theorem. This results in a radius for Spirit Guardian that will most closely follow the third example you've provided.

As you may have noticed, this approach does not strictly match the first rule. The speed and ease of the optional strategy, however, is great enough that my groups have almost always found it preferable to the standard rule.

• Why would the rules around movement cost be the same for this? Can you support that? Commented Mar 2, 2020 at 16:40
• The optional rule on diagonals in the DMG actually says "When measuring range or moving diagonally on a grid, the first diagonal square counts as 5 feet, but the second diagonal square counts as 10 feet. ". That's much more relevant (and removes the house rule bit) regarding range. Commented Mar 2, 2020 at 18:48
• @NautArch man I need to brush up on my DMG knowledge! Turns out the rule I've been using has been official all along. Thanks. Commented Mar 2, 2020 at 19:58
• You might also want to cite/quote the relevant parts from the XGtE setion. Commented Mar 3, 2020 at 3:57
• RAW, Sword Burst would only hit creatures sharing your space: "Range: Self (5-foot radius)". Thus, your second method must be closer to RAI as the description is similar to other range-of-self circular effects: "All other creatures within 5 feet of you must succeed on a Dexterity saving throw or..." Commented Oct 25, 2021 at 15:45