Do you round up or down?

When not otherwise stated, do you round fractional totals up or down?
For some reason we can't recall, my troupe and I always round up.
I just tried looking up if this is actually in the RAW, and could find nothing.

Depends on what's going on.

Edit - it seems I am indeed wrong - you round up with Affinities! Oops!
If you're talking about Affinity, the cost of xp rounds against the character - so to get 5 xp you have to spend 4 (+ 50% = 6), because spending 3 doesn't get you to 5 (3 + 50% = 4.5, not = 5.) 4 1/2 xp is not 5 xp, and you need 5.

Same (dropping fractions) for partial seasons of study where some fraction of the Study Total is lost - altho' that is less clear, and could easily go either way.

... and I'm drawing a blank when else you'd get "fractions"... :confused:

Calculating Spontaneous Casting Totals. Calculating the amount of vis extracted in a season. Calculating Living Condition Modifier for a Longevity Potion.

(In these cases you round up, which it does state in the RAW, for these circumstances).

Spontaneous spell totals? When dividing, I always round those down, but I can't remember if that's stated anywhere. Form resistance gets divided by 5, and I round that down too.

You might want to consult the ArM5 rules. They directly and explicitly contradict your statement. If you put 3 experience into Creo and have Affinity w/ Creo you get 5 experience in Creo.


I'm not sure if there's anywhere in the books that say to round down. There are numerous instances where the rules explicitly say to round up. For example, you explicitly round up when determining

  1. the magnitude of a spell,
  2. the vis used for a longevity ritual,
  3. determining the bonus from a longevity ritual,
  4. experience from Affinity w/ Art,
  5. the maximum bonus for exceptionally crafted objects,
  6. the vis used to bond a familiar,
  7. the amount of vis extracted from an aura, and
    8 ) the amount added to an aging roll based on actual age.

Included above we have dividing by 2, 3, 5, and 10 all rounding up. I do not recall reading any rounding down, though it wouldn't surprise me to find examples. Anyone seen one? However, since we saw so many examples of rounding up our troupe always rounds up. If we find a statement about rounding something down, we will, but not until then.


The rules explicitly state that form resistance is rounded up. (ArM5 p.77.)


Yup, standard everywhere its mentioned in AM is to round up IIRC.

Nope, none that i can recall anywhere.

In AM5, as the rules are heavily in the direction of rounding up, that is the standard.

Outside of AM (ie other games), i usually go by the rule that if its .5 or above, round up, if its <.5 round down.

I'm pretty certain Form Resistance gets rounded up in RAW. So having a Form Score of 1 is of benefit.

On second thoughts, I'm not sure that anything is stated in RAW about the rounding of Spontaneous spell totals.

Always round up, because .5 is close to the next number and because i don't recall any specific rule doing the opposite.

One of the good and amusing things about D&D 3.x/4 is that it's stated very clearly, as one of the three (or so) basic rules indeed, that you always round down (or was it up? It's been a while - anyway, in one direction). That serves to avoid so much confusion, and ArM has even more dividing going on.

Actually, Idid consult them before posting - and Affinity with Ability says nothing on it - zero. Only Affinity with Art (the later listing) says to round up, (which I of course didn't read). But if one, then I'd believe both.

We round up. Each time that the book says "or fraction" it mentions that fractions count (round up). So we always round up if we get a decimal number.


For spontaneous spell totals I don't round at all (never have in any previous edition either). I end up with fractional spell levels and I've never have had a problem with it, the results are, for the most part, similar to the more complex process of rounding down.

I ask myself up to four questions when it comes to rounding: If question one answers my problem, I do not think about question two etc.

I first ask myself:

Is it necessary to round? For stressful spontaneous, it is not: If you have 9,5 and you need 10 - you do not succeed. If the sg is nice, you may have a partial success, but that is sg overriding the rules.

Then I ask myself:

Are there rules that govern rounding?

Sometimes there are (e.g. form scores, number of tractatus one can write).

I ask myself: Is it unfair always to round up (that is affinities mostly). I then round up, then down, then up then down. I start with up though.

Is it smaller than .5?
That means rounding down.

As I noted earlier,
9) form resistance.

And I have now found a round-down listed in the books! It's in RoP:TI. Round down to find:

  1. the points acquired from Ablating.