BECMI Magic missile issue

Hello, I am actually playing BECMI D&D and I was wondering if there is a way to auto-calculate the number of magic missiles available to cast. The rule says: For each 5 levels the caster has above 1st, two more missiles are created (i.e. 1 missile at 1st level, 3 missiles at 6th level, 5 missiles at 11th...) The macro I am actually using for this spell prompts the level of the caster (1-5, 6-10, 11-15 and so on) in order to know how many missiles are available, but I would like to automate this step with the @{level} attribute, if possible. While recalling some easy math formula, I came out with something like [[0.4*@{level}+0.6]] but I soon realized it only works if you are at 6th, 11th, 16th level and on, not in the levels between since I'm dealing with a step function. How should I fix it in order to make it always work, no matter the level you are on?

Something like this is what you want: [[1 + floor((@{level}-1)/5)*2]] If you start with the level step - in this case it's 5. So at the core of it you'll need floor( @{level} / 5 ). But we want the first tick to be at level 6, not at 5, so it becomes floor( (@{level}-1) / 5 ) This gives the correct level bumps, but it's an increase of 2 each time, so multiply that whole thing by 2: floor( (@{level}-1) / 5 )*2 And then just add the default 1 missile from levels 1-5: [[ 1 + floor( (@{level}-1) / 5 )*2 ]] Or... you can use ceiling instead of floor: [[ ceil( @{level}/5 )*2 - 1 ]] Similar theory - start in the middle with your rounding, and work it out from there. In this case ceil( @{level / 5 ) already works by giving us the first increase at level 6, making it a bit simpler.

I was completely out of track on this! Now I got it, thank you Oosh very much for the step-by-step explanation :-)