Reach, Is it really longer than it appears?


Rules Questions


My DM seems to believe a Purple Worm which has a 15ft reach, can strike at a creature 3 Squares (15 ft) but 4 Squares (20ft) in the air. Paizo does not factor in a creature's size as additional reach. Purple Worm is Gargantuan, its size grants it a 15 ft reach. I should be not attacked by my DM insists it can. This created a rather large argument. He seems to think this giant monster can attack an additional 15ft when it can't, as its reach regardless of size is 15ft. Am I right or am I wrong?

By this logic, an 6 ft tall human wielding a 5ft long blade should technically have 10ft reach if the height of a creature matters.

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It's not super clear, but assuming most monsters are cubes is a fairly normal thing IME. That means a Huge purple worm actually takes up space 15 feet up, so if you're 20 feet up you're only five feet away from it.


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A Gargantuan creature occupies a 20'x20' footprint, so in a horizontal plane we have
.
.
.
.
.
.
WWWWrrrs
WWWWrrrs
WWWWrrrs
WWWWrrrs

W = worm, r = within reach of worm, s = safe.

Then we examine the vertical axis. Remember that reach is always measured from the nearest surface of the creature. While creatures are not necessarily cubes (IIRC), a Gargantuan creature is going to be at least 10'-15' high, which means something 20' up is only 5'-10' away from the worm, well within its 15' reach. If we treat the worm as a cube, something 20' up is actually adjacent to it.

To be out of reach of the worm you need to be 20' away from its closest surface, so *40'* from the ground if the worm's a cube, just as you'd need to be 40' away from the left-hand margin in my horizontal diagram to be out of its reach there.


ryric wrote:

It's not super clear, but assuming most monsters are cubes is a fairly normal thing IME. That means a Huge purple worm actually takes up space 15 feet up, so if you're 20 feet up you're only five feet away from it.

but that is incorrect, because it only has a 15ft reac, not a 25 or 30 ft reach. by that logic i could be 3 squares away but 100 ft up and it still reach me. that's incorrect as well.


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It doesn't have infinite reach upwards, but it will be able to reach more than 15 feet off tye ground.

A normal human-sized character takes up one 5-foot cube, and has 5-foot reach, meaning they can attack someone hovering 5 feet off the ground (they can attack someone in the cube above them).

A large sized humanoid takes up a 10x10x10 cube, and has 10 feet of reach, so they can attack someone hovering 15 feet above the ground (inside the cube that ends 20 feet up).

A Huge sized humanoid would occupy a 15x15x15 cube, and have 15 foot reach, meaning they could attack someone hovering 25 feet above the ground (inside the cube that ends 30 feet above the ground).

Basically your space plus reach is how high you can attack someone.

In the case of a purple worm, it has space 20, reach 15, so it will be able to attack someone hovering 30 feet off the ground (in the cube that ends 35 feet off the ground). This of course assumes they're attacking directly upwards, diagonal cubes losing some reach.

If you were intending to fly above the worm out of its reach and simply misunderstood the description then the GM should be lenient (as their description may be at fault), but if you're within a 30 foot high chamber trying to fly over it then you're out of luck.


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Danzibe1989 wrote:
ryric wrote:

It's not super clear, but assuming most monsters are cubes is a fairly normal thing IME. That means a Huge purple worm actually takes up space 15 feet up, so if you're 20 feet up you're only five feet away from it.

but that is incorrect, because it only has a 15ft reac, not a 25 or 30 ft reach. by that logic i could be 3 squares away but 100 ft up and it still reach me. that's incorrect as well.

You’re misunderstanding. The assumption made is that a creature of space 15 feet also stands 15 feet tall, and its reach is measured upwards from that height, so you at an altitude of 20 feet are lower than the (15+15=30) total height the creature can reach to. If you were 100 feet up, it could not reach you,


I would say it should be pretty apparent to your PC that 20' was not safe - you shouldn't float into the worm's airspace and be completely blindsided that it can reach you at 20' up.


I have always run it as "vertical reach is measured from how tall you are" so you can have a human with a polearm attack something 15' above the floor if it is directly above them- all they need to do is reach up.

So I would not say 20' up is not safe from the worm. Where the ambiguity lies is "how many 5' cubes does the purple worm take up vertically". It is probably wider than it is tall, but it should be at least 5' high.


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Were you 20' above the ground?

Or 20' above the worm?

There's a gargantuan difference between the two... literally.

20' above the ground means you are adjacent to the worm, even if you are flying above it, you can actually stand on its back at this point.

20' above the worm means that you are 40' above the ground.


Another way to say what everyone is saying is that you calculate reach from any edge of the creature's space, not from its center. So a creature (regardless of size) with 15 ft reach would be able to reach all of the squares in its space as well as anything within 3 squares of its space. You would have to be 20 ft (4 squares) above the top of the worm to be out of reach.
However, as someone pointed out, it would generally be obvious that the worm could reach you if you were right on top of it; the GM should have said (when you were about to move adjacent to it above) that you would definitely be within reach. BTW it also works both ways; usually to target a creature you only need one of its squares in range.

Dark Archive

20' above the worms head, or 20' above the ground?

A gargantuan creature is 20' tall and with a reach of 15' it could hit you if you were as much as 35' above the ground.


Danzibe1989 wrote:
ryric wrote:

It's not super clear, but assuming most monsters are cubes is a fairly normal thing IME. That means a Huge purple worm actually takes up space 15 feet up, so if you're 20 feet up you're only five feet away from it.

but that is incorrect, because it only has a 15ft reac, not a 25 or 30 ft reach. by that logic i could be 3 squares away but 100 ft up and it still reach me. that's incorrect as well.

You're understanding of size of reach seems to be incorrect.

Reach is how far away you can attack. Size is how much space you take up.

You measure your reach distance from the squares you take up.

As an example, a medium sized character with 5ft reach occupies 1 5ft cube. It can reach 5ft away, so the character has an "envelope" of 10ft.

If you give them a reach weapon, they would have a 15ft "envelope".

A large creature takes up a 10ft by 10 ft cube. They normally have 10ft reach. This means they have an "envelope" of 20ft. If they have a reach weapon, that doubles their reach to 20ft. They have an envelope of 30ft then.

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