D&D General Why do we Round Down???

[LadyElect]

At least with regard to calculating ability score modifiers, I imagine it’s to give 20 some meaning.

 

[Charlaquin]

In 2E we used to keep the half points, but they didn't count towards your active HP. It was so you gained the correct average every two levels. If you'd gain a 1d8, for example, the average would give you 4 then 5 HP over two levels. 5E makes it simpler, but I dislike the fact that it's statistically better to just take the average every time.

If you reroll 1s, you get the same average as if you take the half-rounded-up value.

 

[pming]

I'm mostly curious about 5e but tagging this General because "always round down" is such a longstanding tradition in D&D.

What's the point? Why not "always round the way your 3rd-grade math teacher taught you?"

As far as I can tell, the main effect that "always round down" has on the game is that dealing half damage benefits the defender... to the tune of 1 point of damage, 50% of the time. Well, that, plus an annoying amount of "(round up)" exceptions throughout the text.

Thoughts?

Because, to my utter disgust and dismay, when I've DM'ed a couple new players for one-offs or running them through character creation (doesn't matter what RPG), it goes like this 9/10 times.
..
Me: "Add STR + CON, divide by two"
Them: "Round up or down?"
Me: "Just round it normally"
Them: "Huh? So, up then?"
Me: "No, not up or down, just how you normally round numbers when getting a remainder"
Them: "I don't get it. You have to round up or down"
Me: sigh
..
That's, unfortunately, been my experience over the last 20'ish years. Oddly enough, before that, it was more rare. I'd say... about 2001 or 2002 was the start. Very strange. Only conclusion I can come to is that Schooling has become... "lax".

I've used "ru" and "rd" when writing stuff down on a character sheet sheet for various games to clarify for my players. If they don't see either, then they assume they should keep 2 decimal places. (i.e., "X+Y/3 (ru)" for rounding up).

^_^

Paul L. Ming

 

[Umbran]

Because, to my utter disgust and dismay, when I've DM'ed a couple new players for one-offs or running them through character creation (doesn't matter what RPG), it goes like this 9/10 times.
..
Me: "Add STR + CON, divide by two"
Them: "Round up or down?"
Me: "Just round it normally"
Them: "Huh? So, up then?"
Me: "No, not up or down, just how you normally round numbers when getting a remainder"

When you are dividing by two, and have to round, rounding normally is rounding up.

 

[Radaceus]

How about, if the roll is with Advantage: round up, otherwise: round down

just to keep it in line with our understanding of the fractional functions of 5E

 

[77IM]

Are there really that many ? I honestly cannot recall even one, but I'm sure you'll let us know.

There are only a couple of "(round up)" rules in the PHB, but supplements have more of them, and third-party stuff is rotten with them, especially variant class and race features.

It's just an annoying little thing that I'd rather not have to think about, especially since it serves so no apparent purpose.

 

[Azzy]

In the sciences you're supposed to round to evens (1.5 and 2.5 both round to 2) to average out those effects.

That's to account for rounding bias. However, rounding bias isn't really a thing that occurs when rounding in D&D where such bias actually has a statistically significant or meaningful effect.

 

[Azzy]

I'm mostly curious about 5e but tagging this General because "always round down" is such a longstanding tradition in D&D.

What's the point? Why not "always round the way your 3rd-grade math teacher taught you?"

As far as I can tell, the main effect that "always round down" has on the game is that dealing half damage benefits the defender... to the tune of 1 point of damage, 50% of the time. Well, that, plus an annoying amount of "(round up)" exceptions throughout the text.

Thoughts?

I've wondered this many times before and it always annoys me.

As an interesting (maybe not) anectote, in the Hero Sysyem, you always round x.5 in whichever way benefits the player character.

I still prefer standard rounding (where x.5 rounds up), though.

 

[Lyxen]

There are only a couple of "(round up)" rules in the PHB, but supplements have more of them, and third-party stuff is rotten with them, especially variant class and race features.

It's just an annoying little thing that I'd rather not have to think about, especially since it serves so no apparent purpose.

Can you please give some examples here ? Because, as I've said, I can't recall any, and you seem to find that there are a lot, or at least a couple, in the PH alone...

 

[embee]

In 2E we used to keep the half points, but they didn't count towards your active HP. It was so you gained the correct average every two levels. If you'd gain a 1d8, for example, the average would give you 4 then 5 HP over two levels. 5E makes it simpler, but I dislike the fact that it's statistically better to just take the average every time.

I dunno. Seems like a bad idea to me.

I mean, what's to stop someone from coming up with some spell that takes all those fractional HPs and stores them in some secret Bag of Holding?