Does Maximum HP remain the same when characters level up?

[Clever_Munkey]

I've seen it in some games but never as a Houserule for "mayor" OSR games
You roll your new HD and if its lower you increase your HP by 1.

Stars Without Number does this RAW. It's done, but not super common.

[Tweeker]

I will add that, while not by the book, it's always been a very common and popular house rule to re-roll all the HD when a character levels up and to take the higher value. In practice this gives the character a very small survivability boost.

I had not heard of this practice, but I was thinking of making it a house rule.

[Tweeker]

I looked at the numbers, and it seems it would only give you on average about 0.8hp/level,

Screenshot 2021-01-07 010331.png (35.02 KiB) Viewed 3168 times

I used to give my players "0 level" hit points, an extra 1d8 starting hit points on the assumption that the had been townsfolk before they became adventurers. That would be worth less at level 10, but more at low levels.

Screenshot 2021-01-07 011359.png (53.92 KiB) Viewed 3168 times

[Tazer_The_Yoot]

I will add that, while not by the book, it's always been a very common and popular house rule to re-roll all the HD when a character levels up and to take the higher value. In practice this gives the character a very small survivability boost.

I had not heard of this practice, but I was thinking of making it a house rule.

It's a fairly popular house rule. It's based on one of Gary Gygax's house rules. Another similar one I've heard of is rolling all HD again after an extended rest or a powerful healing spell or potion. Again, these are house rules and mere suggestions for slightly different campaigns, not official BFRPG rules.

[Traveller]

I looked at the numbers, and it seems it would only give you on average about 0.8hp/level,

Thanks for the very clear graphs. Another option to add to the mix is start at Max HP at level 1.
Graph-wise it is the regular method shifted 2.5 point up (right?).
Eye-balling your last graph, it looks it will go under the "re-roll" method just before 4th level.

[Tweeker]

That would be about right for a 1st level Cleric, Thieves and Magic Users on the other hand would only gain an extra 1.5 hit points. At max hit points they still have only 4 hp, and can be killed in 1 swing by any random orc, goblin, or kobold.
.
I can understand the reasons you might not want mage to have too many extra hit points, but I also don't like 1 hit kills. Ideally characters should start with at least 5 hit points, if you are limiting the encounters to monsters that do 1d4 damage. Otherwise every combat is a 1 hit kill situation for thieves and mages. Giving the characters a few extra hit points at low levels helps prevent this, and as they rise in levels the classes will diverge in their resiliency. If you want to maintain the differentiation between the classes you could give each class a different bonus, mages and thieves get +4 hp, clerics get +5 and fighters get +6, that all way player are guaranteed to survive 1 hit from a low level creature doing 1d4 damage. 2 hits can still kill them about 9.25% of the time, but fighters can soak up more damage, likely 3-5 hits, a second hit will only kill a fighter 4.3% of the time.

[Seven]

I deal with the one-hit-kill situation with the optional rule of dying at -10 while being unconscious and losing 1 hit point per round after reaching 0 or below.