Premise: I know that houseruling retroactive skill points would prevent this from being a problem.
I'm aware of the possibility. It just isn't what is true for most characters I make.

This question stems from my optimization obsession. Whenever I build my characters I always try to get the best I can from the build I chose. A suboptimal barbarian/fighter half-elf, for instance, would always start with the barbarian level for the increased HP and skill points.

This question is about one of those times where the order at which you gain things changes the final result: the non retroactiveness of skill point gains and the interactions between money gain and buying magical tomes.

Tomes of Clear Thought (or wish spells) are a strange beast. They're one of the few ways to increase your ability point gain, but every time you spend money on them you start from scratch - meaning your actual inherent bonus doesn't matter, if you want a +5 you need to pay the same sum no matter if you started from a +0 or a +4.

Moneywise, it's more efficient to wait until one can buy a +5 book (or a +4, if a +5 would get an odd Int score) and do all the upgrading at once.
Skill-points-wise, I'm pretty sure that's not the case.

Let's say you can buy a +5 book at level 13, and you started from an odd score. When you get to level 14, you gain 3 more SP. Now, what if your wealth allowed you to buy a +3 book at level 12, meaning you would have less money at level 13 and a +5 could only be bought at level 14? You would have gotten 2 extra AP at level 13, 2 more at level 14, totalling 4 more by the same level.

I'm looking for an optimum-finding procedure (which I'm going to transform into a fillable spreadsheet) that considers those inputs:

  • the money the character gets at every level - according to the WBL table or to the next row of it (since you can be 1XP removed from the next level and with all the money already, buy the tome and wait a week before leveling up)
  • whether your DM tells you you can spend all your WBL on a single object or not (this is usually done at character creation only, but I'll probably need it to be true for every level up to the one I'm building my character at), including the allowed percentage and the level at which the character is built.
  • whether the starting Int value is even or odd (it will usually be odd, to actually benefit from a +5 tome. Sometimes a high roll and a desire not to lose physical stats due to age category shifting or starting with an old character will make it even regardless, and also see below). Notice how this actually splits the problem in two, one with odd books and one with even ones.

It's already been determined that every age increase that's deemed to be desirable on the build should be done as soon as possible (level-wise. I don't expect people to age before time) since it has no cost and it can only improve the gains. If the starting Int with the age bonus included turns out to be odd, the aging can then be delayed until the first tome is bought but not later (otherwise one would need to buy a larger tome, possibly shifting one of the next purchases up a level), but the math has to be done considering the bonus already there.

The optimization should also take the following into account:

  • sometimes, the resources your build can put into a starting Intelligence score are poor and reaching a odd score (e.g. 15) is not possible. Is the extra early skill points gained by starting from an even score (14) a net gain compared to starting from a lower odd score (13)? An odd score means being able to purchase your first books earlier, after all.

I'm not interested in Int gains from leveling up, because this is for characters that do not otherwise need that much Int, which means those every-fourth-level resources will be spent elsewhere, but I'm probably going to ask a second question itroducing the extra complexity once I have a valid answer to this one.

  • \$\begingroup\$ @Zachiel - I guess that makes sense. Unlimited money does make this make much more sense. \$\endgroup\$
    – Bobson
    Aug 29, 2014 at 20:26
  • \$\begingroup\$ @HeyICanChan It's still a pain, even with temporary damage and you definitely need to have a way to determine which skills are lost in case they need to make a check before they get fixed. The alternative would be to just rule that they don't lose the points, but can't gain any more until they've "caught up". That's probably the easiest way to deal with it. \$\endgroup\$
    – Perkins
    Aug 29, 2014 at 20:32
  • \$\begingroup\$ @Perkins Having thought about this further, I'm not sure skill points are lost upon negative Intelligence modification. Those skill points are already spent. Losing the Intelligence score doesn't take them away like losing a level does, nor does gaining Intelligence give more. Should this be a question so as to not fill up Zachiel's commentspace anymore? \$\endgroup\$ Aug 29, 2014 at 20:37
  • \$\begingroup\$ @HeyICanChan That's precisely why skill points aren't retroactive, as you asked. The bookwork to keep them balanced if they are is just too much of a headache. :) \$\endgroup\$
    – Perkins
    Aug 29, 2014 at 21:13

1 Answer 1


I've built a good start on a spreadsheet to determine this. It only supports one set of options at a time, and you have to manually decide when to buy each book, but it helps with the calculations and you're welcome to expand on it.

Dropbox link


You should only need to edit the green boxes.

  • IsOdd determines whether you're starting from an odd stat or an even one.
  • Investment Max % is how much you're allowed to spend of your wealth on a single purchase. At 100 (as it is in the screenshot), you can spend every copper you have, as demonstrated at level 12. At 50, you'd only be able to spend half of what you have, etc.
  • The Purchase column is where you enter the bonus from a stat book you just bought.

  • The Can afford column tells you the most expensive book you can afford right now. All wealth amounts are based on what you'd end the level with (which is why it starts at 7-going-on-8).


Some preliminary results, assuming 100% investment.

If your stat is ODD, buying books as soon as you can afford an upgrade will cost you 247500 and give you 28 skill points. Saving up and buying a +5 ASAP, you'll only pay 137500 and end up with 24 skill points.

If your stat is EVEN, buying books as soon as you can afford an upgrade will cost you 165000 and give you 18 skill points. Saving up and buying a +4 ASAP, you'll only pay 110000 and still end up with 18 skill points.

  • \$\begingroup\$ Nice sheet. The CanAfford column is probably the best solution to easily deal with the problem without further automatization. I will surely tinker with the file to add some other feature and do some other test like buying +1 then +5 or +3 then +5. \$\endgroup\$
    – Zachiel
    Aug 29, 2014 at 20:31
  • \$\begingroup\$ I suggest column N to be =TRUNC((M3+$Q$3)/2)+N2, with Q3 being "initial Int" so that it can be set to 2 for comparisions where the difference between even and odds means a huge skill point difference in the first levels (as for my last edit of the question). This of course means extending the table to the low levels and adding the 4x gain at level 1. \$\endgroup\$
    – Zachiel
    Aug 29, 2014 at 20:53
  • \$\begingroup\$ I have made some upgrades to your file and now, save for automatically telling me the best option, the file gives me all the info I asked for and even more. Plus, with little tweaking, it could work even with the extra points every 4th level (but it would need trying all 16 tome combinations one at a time). I can't save it in the same format: can you read .ods? \$\endgroup\$
    – Zachiel
    Aug 29, 2014 at 22:48
  • \$\begingroup\$ @Zachiel - Ooh, sounds useful. I should be able to, yes. \$\endgroup\$
    – Bobson
    Aug 29, 2014 at 23:06
  • \$\begingroup\$ Hmmmm (looking at the screenshot again) if I purchase a book at level 8 I only get the first rewards from level 9, right? \$\endgroup\$
    – Zachiel
    Aug 30, 2014 at 0:34

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