Traveller → Percentile Conversion (40–80 Model)

Skill Ladder

Skill-0 → 40%
Skill-1 → 50%
Skill-2 → 60%
Skill-3 → 70%
Skill-4 → 80%

• Skill-0 is required to attempt a task.
• Untrained characters cannot roll.
• Jack-of-All-Trades grants Skill-0 (40%) in all skills.

Base Skill Formula: Base Skill% = 40 + (10 × Skill Level)

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Characteristic Modifiers (DM Conversion)

Percentile Conversion Rule

Each +1 DM = +10%
Each –1 DM = –10%

Converted Table

DM –3 → –30%
DM –2 → –20%
DM –1 → –10%
DM 0 → ±0%
DM +1 → +10%
DM +2 → +20%
DM +3 → +30%

Apply this modifier to the skill percentage before the 90% final cap.

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Difficulty Modifiers

Simple → +20% (or automatic if no meaningful consequence)
Standard → ±0%
Difficult → –20%
Very Difficult → –30%
Formidable → –40%

Difficulty modifiers apply to the final percentage calculation.

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Final Calculation

Final% = Base Skill% + Stat Bonus% + Difficulty Mod%

Apply 90% cap after all modifiers.

Final% = min(90, max(0, total))

Roll d100.
Success if roll ≤ Final%.

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Design Principles Preserved

• Skill-0 required to attempt.
• Stats meaningfully affect outcomes.
• Experts are strong but not automatic.
• High difficulty meaningfully pressures low-skill characters.
• Final success chance capped at 90%.