D&D 5E (2014) DMG page 274.

[UngeheuerLich]

45 hp for CR 1/8 seems way too high if it is average...

Is it adjusted for AC?

 

[aramis erak]

[MENTION=53176]Leatherhead[/MENTION], I want to be able to use these guidelines to create monsters that look like the ones in the Monster Manual. Which means that I need a way to determine the appropriate number of hit points for a monster of my chosen CR and how to use that amount of hp to determine their number of Hit Dice. Until we know for sure whether or not the range listed on that table is supposed to be a monster's average HP or their typical HP potential, I can't really do that, because I don't know which approach the designers of the game had in mind when they built their own monsters.

To be clear, I understand your explanations above perfectly well. And using that table's range as "whatever this particular monster's hp is" works perfectly fine for determining CR on the fly, during preparation for an adventure or during gameplay. But unfortunately, it doesn't help anyone looking at this from the standpoint of monster design. For that, we need to know what the designers intended... which is why an official answer would be really useful at this time.



Oh, cool. Anyone care to send him a Twitter message?

You're stuck looking at this from a prior edition mentality, and it's blinding you.

Every monster in the MM and the DMBR has a fixed number of HP. The roll is parenthesized; this implies quite strongly it's not the default mode. (By implies quite strongly, I mean, its about as strongly as a hand out with a pistol aimed at your head implies a mugging.)

In the same way, the default mode by the rules for damage for monsters is their average damage. (p 278)

Likewise, every monster I checked had a HP range that was wider than the CR bracket the average fell into.

For example, none of the bears have a HP range sufficient for their CR; they the brown and black have an average HP in the CR 1/8 range, and AC's in the CR0 range. The Polar Bear has a listed 42 HP (CR 1/4), the potential range of HP is 20-65 - Cr1/8 to Cr 1

Few of the low end critters in the PHB or MM appendices have ranges of HP within a single bracket from the table.

 

[Tormyr]

The HP range and DPR range are intended for the averages, but they work for whichever method you use. If you want to use the maximum value on on the hit dice, take that total, compute the effective HP based on resistances, immunities, and anything else and calculate the final CR off of that. If you roll hit points, find out where it ended up, calculate effective HP and calculate the final CR.

But save yourself some grief and just choose one. It doesn't matter which method you choose. The final CR is calculated after that step anyway.

 

[Leatherhead]

45 hp for CR 1/8 seems way too high if it is average...

Is it adjusted for AC?

Yes. And DPR too.

 

[Grazzt]

Yes. And DPR too.

And even then, there's some other tweaking going on not found on the tables, which much like last edition and PF means eyeballing it and playtesting the crap out of it til it feels right.

For example, try building the MM Ogre from the tables. It doesn't line up. CR for DPR is 1. HP is like CR 1/4. AC is less than that. By the "rules" it shouldn't be CR 2 at all. (Unless I missed something jacking its CR up but I don't think so as it doesn't have immunities, resistances, or saves that modify it's effective AC or hp.)

There are other examples to that won't fit if you try to rebuild MM 1:1, so best thing to do is build it. Play it. See if it works. Adjust on the fly if needed to get it right.

 

[JEB]

You're stuck looking at this from a prior edition mentality, and it's blinding you.

Glad to see you're not trying to make this personal!

the default mode by the rules for damage for monsters is their average damage. (p 278)

Ah, very good find. That does seem to heavily imply HP follows the same rules. If only they'd actually said so, then we wouldn't have to assume...

As such, I took the plunge and got a Twitter account, so I could ask Jeremy Crawford for a clarification. Hopefully he'll respond, and soon.

Likewise, every monster I checked had a HP range that was wider than the CR bracket the average fell into.

Yeah, I've started to notice that too. In fact, the HP range for actual monsters almost never seems to fit what they give us for that CR on p. 274. Even though the Defensive CR is supposed to factor that in.

BTW, your equation works fine for either approach on estimating HD, so long as you're not using one to determine the other like I did by mistake. I went ahead and remodeled my spreadsheet using that, and credited you in my G+ post. Thanks for sharing that with us!

 

[Tormyr]

And even then, there's some other tweaking going on not found on the tables, which much like last edition and PF means eyeballing it and playtesting the crap out of it til it feels right.

For example, try building the MM Ogre from the tables. It doesn't line up. CR for DPR is 1. HP is like CR 1/4. AC is less than that. By the "rules" it shouldn't be CR 2 at all. (Unless I missed something jacking its CR up but I don't think so as it doesn't have immunities, resistances, or saves that modify it's effective AC or hp.)

There are other examples to that won't fit if you try to rebuild MM 1:1, so best thing to do is build it. Play it. See if it works. Adjust on the fly if needed to get it right.

I think the simple answer for the Ogre is that its average damage can kill some level 1 characters outright. It then falls into the "strongly consider things before using this on anyone below level 2" camp.

EDIT: Taking a closer look at the Ogre, the CR for HP is 1/2. The AC of 11 is 2 less than the suggested AC of 13, so the Defensive CR drops to 1/4.
The DPR of 13 suggests an Offensive CR of 1, but the +6 attack bonus is 3 higher than the suggested attack bonus. Normally that would mean that the Offensive CR would go to 2.

The Average of the Offensive and Defensive CR is (1/4 + 2) / 2 = 2.25 / 2 = 1.125 which rounds to 1. However, looking at the +6 attack bonus being really high for a CR1 creature and the DPR of 13 being on the high end you could give it an offensive CR of 3, although that does not strictly follow the guidelines. That would make the average 1.625, which rounds up to 2.

 

[Tormyr]

One slightly bizarre aspect of this approach is it means that higher con creatures will have fewer HD than similar challenge lower con creatures. If we're letting monsters use HD like PCs it means that the highest con monsters will have the worst healing abilities.

With the way the monsters in this edition are set up, if you want to give them hit dice for healing, I think it would work better to give them a number of hit dice for healing purposes (not for calculating HP) equal to their CR. A CR 5 creature might have 13 hit dice in calculating its HP, but it would only have 5 hit dice for healing. This would bring it closer in line to the way PCs work (1 hit die for healing per level for a PC and 1 hit die per CR for a creature).

 

[UngeheuerLich]

I don´t have the table, but the hp line, as you describe how it works is really off target if you compare it to the mm.

The clear trend there is:
about 7 hp: CR 1/8
about 11 hp: CR 1/4
about 15-22 hp: CR 1/2
about 30-45 hp: CR 1

I really like to read that paragraph, if something is missing here...

 

[JEB]

I don´t have the table, but the hp line, as you describe how it works is really off target if you compare it to the mm.

The clear trend there is:
about 7 hp: CR 1/8
about 11 hp: CR 1/4
about 15-22 hp: CR 1/2
about 30-45 hp: CR 1

I really like to read that paragraph, if something is missing here...

Yeah, regardless of whether it's average or maximum, the hp numbers in the table seem way higher than the vast majority of monsters of that CR are actually capable of in the MM. Even the Gargantuan, CR 30, Con 30 Tarrasque only has an average of 676 hp, equivalent to a Defensive CR of 27; seems like it would only get dragged up to Defensive CR 30 because of its AC (or more likely, its AC is only 25 because they wanted to justify a CR of 30).

It's almost as if the table is designed to focus on Offensive CR as the more important of the two. That the HP totals there aren't an accurate read of what a monster of that Defensive CR should have, but rather are listed as a tool to adjust the Offensive CR up or down by a limited degree.

(I'd happily share the paragraph with you, but I assume that wouldn't be appropriate, since it's such a big selling point for the book. Sorry. )