Calculation reference
Form Forge ships three calculation types. Each one reads from some fields and writes its result into a target field. This page lists the fields (called "roles") each type needs and the formula it applies. For a step-by-step walk, see Using Form Forge and Saving throws & skill checks.
All calculations follow standard D&D 5e math.
Ability Modifier
Calculates an ability modifier from an ability score.
Formula: modifier = floor((score - 10) / 2)
| Role | Required | What it is |
|---|---|---|
| Ability Score | yes | The base ability score, e.g. STR, DEX |
| Target Modifier | yes | Where the calculated modifier appears |
Saving Throw Modifier
Calculates a saving throw from an ability modifier and proficiency.
Formula: save = abilityModifier + (proficient ? proficiencyBonus : 0)
| Role | Required | What it is |
|---|---|---|
| Ability Modifier | yes | The relevant ability modifier field |
| Proficiency Bonus | yes | The character's proficiency bonus |
| Proficiency | yes | Checkbox indicating proficiency in this save |
| Target Saving Throw | yes | Where the save total appears |
Skill Modifier
Calculates a skill check from an ability modifier and proficiency, with support for expertise and half-proficiency.
Formula: skill = floor(abilityModifier + proficiencyMultiplier * proficiencyBonus)
The proficiency multiplier is 2 with expertise, 1 when proficient, 0.5
with half-proficiency, and 0 otherwise.
| Role | Required | What it is |
|---|---|---|
| Ability Modifier | yes | The relevant ability modifier field, e.g. WISmod for Perception |
| Proficiency Bonus | yes | The character's proficiency bonus |
| Proficiency | yes | Checkbox indicating proficiency in this skill |
| Target Skill | yes | Where the skill total appears |
| Expertise | no | Checkbox for double proficiency (expertise) |
| Half-Prof | no | Checkbox for half proficiency (Jack of All Trades) |