RPG Design: Balancing the books

Perhaps the most involved and frustrating thing to get right when designing an RPG is balancing the numbers. Using dice to represent opposed actions is a suspension of disbelief that only works for as long as the numbers make sense. If they’re unfair or lead to ridiculous results it will undermine the player’s investment in the game. All the numbers are connected in a big web of related scale, so this is going to be a big post. I’ll pepper it with fragments of my suggested rule set, then expand on some of them in future posts. Like a lot of long-lived games, third edition D&D suffered from a problem of gradual escalation of power levels. New classes from a variety of publishers introduced extra options with little central control. Pathfinder has so far remained largely free of this problem by virtue of being more centrally controlled. So enough waffle, onto some specifics.

Vital statistics

The myriad numbers and calculations involved in a character flow from a core set of numbers. You can think of these as equivalent to the axioms in a set of logic: they’re the starting point. In D&D these numbers include:

  • Six ability scores and modifiers. For each ability the score is an absolute measurement of your ability, while the modifier represents your deviation from standard.
  • Base attack bonus is a general figure for how accurately you can hit. This value goes up with your class levels – clearly some classes spend more effort on training for fighting than others.
  • Skill ranks also depend on the class, but you get to choose where to put them. In Pathfinder you get bonus ranks by sticking with your starting class.
  • Class level directly affects a number of calculations. It seems that some things depend on how long you’ve spent on training, not on how well you’ve done.

There are a few things about this that strike me as odd, but perhaps the most important is the speed at which the numbers go up. Six levels is enough to take a character from zero to hero, while typically representing only a few weeks or months of story time (depending on the story). The increases don’t represent the things a character has spent time doing, nor are they tied to effort put into training. Your character could continue to take levels in Wizard without casting a single spell or reading a single tome. I’d therefore like to cut down on is the number of automatically changing scores. Base attack in particular progresses too fast and too automatically for my taste. I’d like to make each level a smaller increment. Many attempts have been made to reduce the set of ability scores, but third edition’s standard six (Strength, Dexterity, Constitution, Intelligence, Wisdom and Charisma) have proven hard to improve on, and they only change slowly so they feel like physical abilities.  There’s a troubling duality though, inherited from older versions of D&D: for each ability, the score has a wide range and an average of 10; while the modifier is that number minus 10, halved. The ability modifier is the one used in almost all calculations, but the score hangs around as a relic of maths past. I’d like to settle on something closer to the modifier as the standard unit. Skills are more mutable: you get a certain number of skill ranks (points) for each level and choose where to spend them. To these are added one of the ability modifiers, as well as various class and circumstance bonuses. Paizo cut down on the list of skills from third edition, and simplified the math slightly. I’d like to do the same, which keeping the same basic nature of skills. What may need clarifying is the role of sub-skills. D&D has a few of these, like track or detect traps. By expanding on the role of sub-skills, I can condense the list of basic skills. This also relates to the skill synergies mechanic from D&D 3.5.

Ability scores

A character has six ability scores: Strength, Dexterity, Constitution, Intelligence, Wisdom and Charisma. These have a range of 2d6 – 5 (from -3 to +7) for PCs at first level, though NPCs, monsters and animals may be higher or lower. An average human would have a score of 0 in all six abilities. Each ability score = 2d6 – 5Ability scores are set at the time the character is created, and only rarely change after that point.Some effects may cause a temporary improvement or detriment to ability scores.


There are a short list of skills in which a character may train. At each level gain skill points equal to your intelligence score, to allocate as you wish. You cannot allocate more points to a single skill than your level. Under each skill is a selection of specialisations. Each time you add a point to a skill, you have the option of adding points to a specialisation. Skill bonus = Ability score + Skill points + Bonuses – Penalties Specialisation bonus = Ability score + Skill points + Extra points + Bonuses – Penalties You cannot use a basic skill untrained. If you attempt to use a sub-skill untrained, you may (at GM’s discretion) use your points in the parent skill. Each skill is associated with an ability score. There is no bonus or penalty for class skills.

Skills will be fixed by the game system. Specialisations are more flexible. The exact list of skills and sub-skills is yet to be nailed down, and sub-skills may depend on campaign, but the list of primary skills will be shorter than in Pathfinder due to a number of skills being merged. It will contain two extra basic skills: Attack and Defend. The purpose of this is to make your progression less automatic. If you concentrate on combat at the expense of other skills, you can progress faster; if you neglect. Here are some possible skills, though this isn’t anything like the final list:

  • Attack
    • Melee attack – STR
    • Ranged attack – DEX
  • Defend – DEX
    • Dodge
    • Counter
  • Agility – DEX+STR
    • Acrobatics
    • Escape
    • Fly
    • Swim
    • Stealth
  • Finesse – DEX
    • Handle device
    • Forge
    • Craft
  • Survival – WIS
    • Track
    • Navigate
    • Handle animal
    • Ride
  • Knowledge – INT
    • History
    • Nature
    • Physics
    • Healing
  • Awareness – WIS
    • Perception
    • Empathy
    • Appraise
  • Social – CHA
    • Persuade
    • Trick
    • Intimidate
  • Perform – CHA
    • Act
    • Sing
    • Dance
  • Magic – CHA
    • Concentrate
    • Decipher magic
    • Ritual

I’d also like to have Languages as a skill with sliding ranks to represent levels of fluency, but I’ll return to that later. There’s one more detail to add, a house rule I encountered once before and liked: rolling a 20 on a skill gives you a chance to gain skills. I like it because it emphasises the skills you actually use and rewards you for playing creatively, while also being a more fair source of bonuses than the GM’s whim. I’ve adapted it to the way I’m using sub-skills.

Natural 20

Each time you roll a natural 20 on a basic skill, you are given the chance to improve that skill. Roll a d20. If the result is higher than your points in that skill (not including ability score or other bonuses) then you get to add a point. Each time you roll a natural 20 on a sub-skill, roll a d20. If the result is higher than the points in that sub-skill, add a point to the sub-skill; if the result is also higher than the combined points of the skill and its parent skill, add a point to the parent skill.

Hit me baby, 147 more times

Hit points are a commonly used abstraction representing a character’s health. When you successfully hit an enemy their number goes down; when it goes down enough they’re dead. Simple, right? Perhaps, but what do hit points actually mean? Untangling the meaning behind hit points matters because  it’s central to simplifying the game system, and because it’s the yardstick against most of the other numbers must be balanced. If basic ability scores are the starting point of calculations, hit points are the end; everything must be in balance for hit points to make sense, and it’s the first symptom when the numbers are First, let’s shove all the computer games out the door, even action RPGs and D&D branded games. We’ll need to set aside the bad habits of  video games if we’re to get to the heart of the matter. It doesn’t make much sense to slice limbs off somebody with a sword until there’s nothing left to chop, or you’d never be able to heal from the injuries so easily, so it’s clear hit points don’t represent physical damage. The metaphor makes more sense in terms of boxing: each hit takes you closer to defeat, and a hard hit makes your defeat so much more likely.  It’s a measure of how much you’ve been worn down by a fight: your stamina, determination, energy, and attention. A character with more hit points can take more of a beating in a fight. So in light of that, does the scale of hit points used by D&D make sense? Compare a second-level bard with 5 hit points and an eighth-level ranger with more than 50 hit points. A hit that would kill the bard wouldn’t even slow the ranger down until he’s taken ten of them. Another problem is the disconnect between hit points and any sort of effect of being worn out. Instead they have a long list of special conditions that are entirely separate: fatigued, exhausted, staggered, stunned, bored, blinded, dazed etc. So here’s my proposal:

Hit points

A character’s hit points start a fixed value, modified for the character’s constitution. They do not automatically increase with each level. Total hit points = 10 + Constitution score A character with fewer 10 hp or less suffers a -2 to all d20 rolls. A character with 5 hp or less suffers a -4 and is limited to a single action each round. A character with 0 hp suffers a -8 and is unable to act. A character with fewer than 0 hp is unable to defend themselves at all.


Some conditions have the effect of making a character temporarily act as if they had fewer hit points. For example, a character with 12 hp who has been stunned for 1 round behaves as if they had only 2 hp, and suffers the appropriate penalties. Some conditions affect only specific senses: a deafened character may not be aware of an incoming enemy, but they can see to hit a point without penalty. Some conditions temporarily boost your hit points. These temporary points are lost first and measured separately from real hit points.

There are two ways of preserving your hit points: avoiding the hit or absorbing the damage. Some roleplaying games model armour as deflecting the hit away, others as reducing the damage you take. Real armour does both, but to keep the numbers in balance we must carefully limit the amount by which the Attack and Defence skills are modified.

You can shoot how many arrows a second?

In between those two sets are the real combat numbers. This is the real test of balance: if the numbers are out of kilter, this is where it’ll show. If a typical attack roll for a given level are significantly higher than the enemy is capable of defending. So


Both attack and defence are active rolls based on the Attack and Defend skills. Attack = d20 + Attack skill bonus + Weapon bonus Defend = d20 + Defend skill bonus + Armour deflection Lesser NPCs typically take a 10 on both attack and defence. Attacking may use the Melee or Ranged attack sub-skills. To use an unfamiliar weapon, resort to the basic Attack skill.

So when a PC attacks a monster, the PC’s attack result may vary between while the monster’s defence stays fixed. When the monster hits back, the monster’s attack is fixed while the PC’s defence varies. If two PCs fight each other, both attack and defence may vary, leading to a wider range of results.

Critical hits

If an attacker rolls a natural 20 (and the attack is otherwise successful), they have a chance of scoring a critical hit. In addition to the weapon’s damage, a critical hit inflicts an effect on the target. The attacker may choose which of the following effects to apply, provided the GM agrees that it makes sense for the situation and weapon used. The defender has a chance to avoid the critical: roll a second attack, and compare its result to a suitable roll made by the defender.

  • Blinded: -4 to Attack and Defend rolls, and to Awareness rolls (Agility roll to negate)
  • Stunned: equivalent to one extra stage of fatigue (Constitution roll to negate)
  • Cornered: defender is throw to floor or against a wall, providing a circumstantial penalty to Defend rolls (Agility roll to evade)
  • Sunder: defender loses grip on a weapon (Finesse roll to negate)
  • Pinned: defender cannot move, takes -2 to Defend rolls (Escape roll to free)

Your character may have additional options, depending on its class, other abilities and equipment.

Saving throwsare D&D’s way of giving you a second chance to avoid something nasty. They represent your ability to dodge, to shrug off an ailment or to maintain your will. These can be simplified by making them equivalent.

Saving throws

A saving throw is any ability or skill roll used defensively to avoid taking damage. You can attempt saves provided you have 0 hp or more, even

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