Dice Formulas & Customization

Read this first (no programming required)

• Formulas are simple, readable expressions (like 2d6+3).
• You can type a formula, roll it, and tap Save Formula to keep it for later. On a phone, Save Formula and Manage Formulas are under the formula field, and on a tablet or desktop they are above it.
• Save stores whatever is currently in the text field and lets you name it and add a description. Manage lets you import, export, rename, reorder, and delete.

Tip: To save, you only need the formula text—no need to understand every option below. Come back here when you want to do something more advanced.

Basics cheat sheet

• Roll dice: XdY (e.g., 2d6, 1d20, 1d% for d100)
• Special dice: 1D66 (uppercase D), 4dF (Fate dice), custom faces: 2d[2,3,5,7]
• Math & grouping: +, -, *, parentheses ( ) (division is not supported)
• Keep / Drop: kh keep highest, kl keep lowest, -H drop highest, -L drop lowest (e.g., 3d20kh2, 4d6-L)
• Explode / Compound: ! (explode), !! (compound), add o for once: !o, !!o (e.g., 4d6!, 5d10!!o>=8)
• Reroll: r (reroll matches), ro (reroll once) (e.g., 4d4r<=2, 4d4ro<2)
• Count / Score:
  • # returns a count and discards the individual dice results: 6d6#>=5
  • #s, #f, #cs, and #cf mark dice as successes, failures, critical successes, and critical failures. The dice and their sum stay as rolled, and the roll row lists the counts. For example: 6d6 #f<=2 #s>=5 #cs6 #cf1
• Clamp (cap): C< and C> (e.g., 4d20 C<5, 4d20 C>15)

Order and precedence gotchas

• Order matters with keep and the marking counters. 2d20 kh #cf #cs drops the low die first, and to mark both dice before the keep you must write (2d20 #cf #cs) kh, because 2d20 #cf #cs kh keeps both dice.
• Drop/filter operators bind tighter than arithmetic. (5d6+5d10)-L2 drops from the combined pool; 5d6+5d10-L2 drops only from the d10s.
• Use uppercase D66 (lowercase d66 is a 66‑sider, not D66).

Patterns you’ll use a lot

• Advantage / Disadvantage: 2d20kh+MOD and 2d20kl+MOD
• Best / Worst of N: NdXkh1 or NdXkl1 (e.g., 3d6kh1)
• Ability scores (4d6 drop lowest): 4d6-L
• Explode once vs. freely: 4d6!o (explode only once) vs 4d6! (repeat)
• Compound (Shadowrun/L5R‑style): 5d6!! or thresholded 5d6!!>=5
• Threshold successes: NdX#>=TN (e.g., 6d6#>=5)
• Reroll once vs. repeat: ro vs r (e.g., 4d6ro1 vs 4d6r1)
• Keep/drop across combined pools: (1d8!!+1d6!!) kh (Savage Worlds trait + wild die)

System starting points (quick recipes)

These examples give you solid starting formulas. Some systems use custom symbol dice—those are noted as “Not supported”.

D&D 5e / Pathfinder 2e

• Attack/check: 1d20+MOD
• Advantage/Disadvantage: 2d20kh+MOD / 2d20kl+MOD
• Ability scores: 4d6-L
• Crits: roll double damage dice manually (e.g., 2d6 → 4d6)

Powered by the Apocalypse (PbtA)

• Core move: 2d6+STAT → interpret 10+, 7–9, 6- manually

Fate Core

• Fate dice: 4dF (already supported)

Blades in the Dark

• Pool take highest: Nd6kh1 (e.g., 3d6kh1)
• Spot crits (two 6s): add Nd6#=6 to count sixes alongside your roll

Shadowrun (hits & glitches)

• Hits: Nd6#>=5
• Track 1s for glitch rules: add Nd6#f=1

Savage Worlds (trait + wild die)

• Roll both, keep highest: (TRAIT!! + 1d6!!) kh + MOD
• Raises (+4) are interpreted manually from the total

Vampire: The Masquerade (V5)

• Successes: Nd10#>=6
• Track 10s: add Nd10#=10 (critical pairs/impacts require table rules)

Call of Cthulhu 7e

• Roll-under: 1d100 vs skill
• Bonus/Penalty dice: handle as a two‑step manual method (tens die replacement not encoded)

Cypher System

• Task roll: 1d20+MOD (step/difficulty remains narrative)

Warhammer/40K‑style d6 pools

• Hits/wounds: Nd6#>=TN (set TN for your table)

Dungeon Crawl Classics (dice chain)

• Odd dice sizes are fine: 1d7, 1d16, 1d24, 1d30

Lancer (accuracy/difficulty)

• Accuracy: 1d20 + (Xd6kh1) + MOD
• Difficulty: 1d20 - (Xd6kh1) + MOD

Year Zero Engine (Free League: Alien, Forbidden Lands, Vaesen, etc.)

• Three colored pools (base/skill, stress, gear): Roll the three pools in one formula with labels, for example “Base”: 4d6 #s=6, “Stress”: 2d6 #s=6, “Gear”: 1d6 #s=6. In Dice Studio the roll shows each pool on its own line with its label and total.
• Successes: Nd6#s=6 on each pool; track 1s on stress/gear with #f=1.
• To push, roll the pool in Dice Studio with a success mark, for example 5d6 #s=6, then use Push on that roll. Push keeps the dice marked as successes and rolls every other die again, including 1s.
• Limitations: Panic/breakage resolution remains table‑side.

The One Ring 2e (approximation)

• Roughly: 1d12 + Nd6
• Notes: Gandalf/Eye and Tengwar sixes are symbol effects; treat specials manually

Legend of the Five Rings

• AEG 1e–4e (Roll & Keep, exploding 10s): Xd10!!khY
• FFG/Edge 5e (symbol dice): Not supported

Genesys / FFG Star Wars (narrative dice)

• Uses custom symbol dice: Not supported

Ironsworn / Starforged

• Action roll: 1d6+MOD vs two challenge dice 2d10 → compare manually (beat both=Strong Hit; one=Weak Hit; none=Miss).
• Progress moves: roll 2d10 vs current progress value (0–10) and compare manually.

Starter downloads

Download sample Saved Formulas for popular systems that are ready to import. Use Manage Formulas → Import. Import adds every formula in the file to the end of your list. It never replaces the list and does not skip formulas you already have. See the Downloads section at the bottom for files.

Important: If you place a file by hand, name it saved_formulas.json and put it in the formulas folder inside the app’s storage folder. That file becomes your whole list. The Import flow does not require a particular file name. In the native apps, the file must end in .json (in any letter case). On the web, the file picker asks for .json files, but the app does not check the extension separately. A file name does not make the contents a valid formula file.

Save, load, import, export (UI recap)

• Mobile: “Save Formula” and “Manage Formulas” are under the formula text field when action buttons are enabled.
• Desktop: both appear above the text field.
• Save adds the current formula to your Saved list and opens a dialog to name/describe it.
• Manage lets you import, export, reorder, rename, and delete.
• Import adds every formula in the file to the end of your list. It never replaces the list and does not skip formulas you already have.

Troubleshooting & gotchas

• My counts look off with advantage
  • Put counters before keep/drop and group them: (2d20 #cf #cs) kh.
• 4d6-L2+2 didn’t do what I expected
  • 4d6-L2+2 and (4d6-L2)+2 are the same roll: drop the two lowest of 4d6, then add 2.
• My D66 looks wrong
  • Use uppercase: 1D66.
• I need exploding “once”
  • Use !o (explode once) or !!o (compound once).
• I want to keep the total but also know successes/failures
  • #s, #f, #cs, and #cf mark dice as successes, failures, critical successes, and critical failures. The dice and their sum stay as rolled, and the roll row lists the counts.

Next steps

• Save your favorite expressions: see “Saving and Managing Dice Formulas”.
• Share and maintain a portable list: see “Formula Schema”.

Syntax engine and docs

The roller uses the app’s own version of Adventuresmith’s dart_dice_parser. The pub.dev page describes the original package, so check a formula in the app before you rely on it. For the full grammar and additional examples, see: https://pub.dev/packages/dart_dice_parser

See a problem?

Help me keep this page and content up-to-date! If you see a problem, please report it: support@jasonholtdigital.com