If this has been reported before, my apologies. Spells that list an area of effect of a sphere with a radius of a certain number of feet have the sphere size set incorrectly. The radius of a sphere is the center point to the perimeter. So a sphere with a radius of 20 feet is 40 feet in diameter (the measurement straight across the sphere. For instance, fireball has a radius of 20 feet which means the area of effect sphere is 40 feet. Whoever input the numbers might need a little refresher in geometry. :D From my brief look at the spell lists, this seems to be an error across the board. Another example is arms of hadar which effects all creatures within 10 feet of the caster. That's a radius of 10 feet and a sphere of 20 feet which it has listed as only a 10 foot sphere.
All 'area' details list radius, not diameter, which is actually geometrically correct as area is based of radius (πr²) rather than diameter.
In game terms, knowing the radius of the spell is more useful to determining it's area than knowing it's diameter.
The fact that all spells a like this, plus that's how the spells describe the area (all spherical spells in 5e are described in terms of their radius) should've clued you in that this isn't an error.
Radius is actually the preferred measurement for doing circular geometry, not diameter
Are you thinking that the 10 and 20 next to the sphere indicate the diameter of the sphere? Because the sphere just indicate the shape of the spell effect. A sphere (in 5e) is always described by its radius and anything that indicates otherwise is the mistake.
So "all spheres use the radius measurement, not the diameter," (paraphrased) is a feature not a bug.
Yes, DxJxC, the sphere symbol made me think it was the measurement of the sphere, not just a part of it. When I looked at other symbols like cubes, lines, and cones, the measurement represents the full geometric shape. So I, wrongly, assumed that spheres were the same. Thanks for the clarification. I'll just remember to double that on spheres to get the full size.
I'm with you on this, as an engineer, saying "20ft sphere" means the sphere 20ft across (as In having a 10ft radius.) The descriptor for range is incorrectly labeled compared to the wording in the spells text. And those arguing the commonality of measurements for sphere, there is neither any evidence for such a statement nor a point, radius is only one of a few ways to do this. 20ft sphere means it's entire width, especially since the shape used is of a sphere, not just a portion of a sphere. It really is poorly done.
It's consistent with the Basic Rules for areas of effect in spellcasting, where the point of origin for a spell's area of effect is stated to be the most important factor.
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Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
I'm with you on this, as an engineer, saying "20ft sphere" means the sphere 20ft across (as In having a 10ft radius.) The descriptor for range is incorrectly labeled compared to the wording in the spells text. And those arguing the commonality of measurements for sphere, there is neither any evidence for such a statement nor a point, radius is only one of a few ways to do this. 20ft sphere means it's entire width, especially since the shape used is of a sphere, not just a portion of a sphere. It really is poorly done.
Luckily, 5e effect descriptions are never so abstract as "20ft sphere," and always describes it as "20-foot-radius sphere." I doubt an engineer such as yourself would ever read that and not know it is 40 feet diameter.
There is only 1 spell that describes a sphere using its diameter and it is also very specific in this case, so there is no chance for confusion.
I have no argument with the full spell descriptions and that they are specific. The point I was originally making was if you look at just the Range/Area line or only look at the Notes listed on the Spells page, you could be misled as a new player. I'm not a new player so I'm familiar with appropriate spell dimensions. However, a new player might not read the spell in full and just see "20 ft." and the sphere symbol. It's a small thing.
As the OP mentioned the issue isn't with the full spell description text, but the simplified stats provided above it all under "Range/Area:" which gives a number then a shape.. which is absolutely misleading. The same thing is what is given in the character sheet when you are looking at your spells as actions. It should properly list the full diameter when doing so.
The sphere symbol is explained in the rules to be a measure of radius, and the rest of the rules use radius when describing spheres. Plus it is a measure from the point of origin at the center. It would just be confusing to have 1 unlabeled symbol mean diameter when diameter is never mentioned in spell effects (which you should be reading, not reading your spells is a classic "bad player" meme).
And regardless of any discussion here, there is nothing DDB can do. They have to use the same format that is in the printed books. In order to fix it, you will have to take it up with WotC and have them change it. Of course that would result in 6 years worth of books that say 20(sphere) and new books that say 40(sphere) existing and being used at the same time. But at least the number 40 would not be mentioned once in the spell description so they will either figure it out or ignore it.
Possibly if the shape image they used in the Range/Area highlighted the point of origin, much like in the image below, and/or had a bold line showing where each length measurement goes (so from a point in the middle of a sphere, but along an edge of a cube.)
That doesn't actually negate the fact that the radius of a sphere is still on half the width of the area affected. Using Radius rather than Diameter doesn't magical make them the same thing.
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If this has been reported before, my apologies. Spells that list an area of effect of a sphere with a radius of a certain number of feet have the sphere size set incorrectly. The radius of a sphere is the center point to the perimeter. So a sphere with a radius of 20 feet is 40 feet in diameter (the measurement straight across the sphere. For instance, fireball has a radius of 20 feet which means the area of effect sphere is 40 feet. Whoever input the numbers might need a little refresher in geometry. :D From my brief look at the spell lists, this seems to be an error across the board. Another example is arms of hadar which effects all creatures within 10 feet of the caster. That's a radius of 10 feet and a sphere of 20 feet which it has listed as only a 10 foot sphere.
All 'area' details list radius, not diameter, which is actually geometrically correct as area is based of radius (πr²) rather than diameter.
In game terms, knowing the radius of the spell is more useful to determining it's area than knowing it's diameter.
The fact that all spells a like this, plus that's how the spells describe the area (all spherical spells in 5e are described in terms of their radius) should've clued you in that this isn't an error.
Radius is actually the preferred measurement for doing circular geometry, not diameter
Find my D&D Beyond articles here
Are you thinking that the 10 and 20 next to the sphere indicate the diameter of the sphere? Because the sphere just indicate the shape of the spell effect. A sphere (in 5e) is always described by its radius and anything that indicates otherwise is the mistake.
So "all spheres use the radius measurement, not the diameter," (paraphrased) is a feature not a bug.
Yes, DxJxC, the sphere symbol made me think it was the measurement of the sphere, not just a part of it. When I looked at other symbols like cubes, lines, and cones, the measurement represents the full geometric shape. So I, wrongly, assumed that spheres were the same. Thanks for the clarification. I'll just remember to double that on spheres to get the full size.
Radius is a measurement of spheres, in fact it's the most common way of describing a sphere.
Find my D&D Beyond articles here
I'm with you on this, as an engineer, saying "20ft sphere" means the sphere 20ft across (as In having a 10ft radius.) The descriptor for range is incorrectly labeled compared to the wording in the spells text. And those arguing the commonality of measurements for sphere, there is neither any evidence for such a statement nor a point, radius is only one of a few ways to do this. 20ft sphere means it's entire width, especially since the shape used is of a sphere, not just a portion of a sphere. It really is poorly done.
It's consistent with the Basic Rules for areas of effect in spellcasting, where the point of origin for a spell's area of effect is stated to be the most important factor.
Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
Luckily, 5e effect descriptions are never so abstract as "20ft sphere," and always describes it as "20-foot-radius sphere." I doubt an engineer such as yourself would ever read that and not know it is 40 feet diameter.
There is only 1 spell that describes a sphere using its diameter and it is also very specific in this case, so there is no chance for confusion.
I have no argument with the full spell descriptions and that they are specific. The point I was originally making was if you look at just the Range/Area line or only look at the Notes listed on the Spells page, you could be misled as a new player. I'm not a new player so I'm familiar with appropriate spell dimensions. However, a new player might not read the spell in full and just see "20 ft." and the sphere symbol. It's a small thing.
As the OP mentioned the issue isn't with the full spell description text, but the simplified stats provided above it all under "Range/Area:" which gives a number then a shape.. which is absolutely misleading. The same thing is what is given in the character sheet when you are looking at your spells as actions. It should properly list the full diameter when doing so.
The sphere symbol is explained in the rules to be a measure of radius, and the rest of the rules use radius when describing spheres. Plus it is a measure from the point of origin at the center. It would just be confusing to have 1 unlabeled symbol mean diameter when diameter is never mentioned in spell effects (which you should be reading, not reading your spells is a classic "bad player" meme).
And regardless of any discussion here, there is nothing DDB can do. They have to use the same format that is in the printed books. In order to fix it, you will have to take it up with WotC and have them change it. Of course that would result in 6 years worth of books that say 20(sphere) and new books that say 40(sphere) existing and being used at the same time. But at least the number 40 would not be mentioned once in the spell description so they will either figure it out or ignore it.
Possibly if the shape image they used in the Range/Area highlighted the point of origin, much like in the image below, and/or had a bold line showing where each length measurement goes (so from a point in the middle of a sphere, but along an edge of a cube.)
Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
I like that!
That doesn't actually negate the fact that the radius of a sphere is still on half the width of the area affected. Using Radius rather than Diameter doesn't magical make them the same thing.