Success Rolls
How the dice decide everything — and when they should
The Success Roll
Whenever a character attempts something with a meaningful chance of failure, the GM calls for a success roll. Roll three six-sided dice (3d6). If the total rolled is less than or equal to the governing number — most often a skill level or attribute — the action succeeds. Roll higher, and it fails.
Mira attempts to pick a lock. Her Lockpicking skill is 12. She rolls 3d6 and gets an 8. Since 8 ≤ 12, she succeeds. If she had rolled a 15, she would fail — that's the whole system.
Coming from D&D? GURPS flips the direction of success. In D&D, rolling high is good. In GURPS, rolling low (under your target number) is good. Think of it as rolling under a percentage skill — except your target is a small number, and the dice are 3d6 instead of d100.
Two Guaranteed Outcomes
No matter what target number you're rolling against, two results are always fixed:
- A roll of 3 or 4 is always a critical success — the best possible outcome.
- A roll of 17 or 18 is always a critical failure — the worst possible outcome.
Even a character with Lockpicking-20 can fumble a lock on a 17. Even a novice with Lockpicking 5 can pull off a miraculous success on a roll of 3.
When to Call for a Roll
The GM should only require a success roll when there is a genuine chance of meaningful failure — not every action deserves dice.
Roll when:
- A character's health, wealth, allies, reputation, or equipment are at risk.
- A character stands to gain information, allies, abilities, or social standing.
- In combat — always, even against stationary targets at point-blank range.
Don't roll for:
- Utterly trivial tasks (crossing the street, feeding a dog).
- Routine day-job work where failure has no consequences.
- Anything a character with that skill level would obviously succeed at.
The GM may roll in secret for two reasons:
- When a character wouldn't know if they succeeded — e.g., Detect Lies, Search, or Sense rolls. On success, give true information; on failure, give none or misinformation.
- When the player shouldn't know what's happening — e.g., an unseen predator in the jungle. The GM rolls secretly; if the character notices, they get the information naturally.
Modifiers & Task Difficulty
+Number = beneficial. −Number = penalty. Modifiers adjust your target number, not the dice roll. A +3 bonus means you roll against 3 higher; a −2 penalty means you roll against 2 lower. Higher target number = easier to succeed.
Base Skill vs. Effective Skill
Your base skill is the raw number on your character sheet — what you paid points to achieve. Your effective skill for any particular attempt is your base skill plus or minus all applicable modifiers for that specific situation.
Mira has Climbing-15 on her sheet. She attempts to scale a vertical stone wall in the dark. The wall gives −3; total darkness gives −9. Her effective skill = 15 − 3 − 9 = 3. She needs a 3 or under on 3d6. Possible, but extremely dangerous.
You cannot attempt a success roll if your effective skill falls below 3 — the task is beyond your ability in those conditions. Exception: active defense rolls in combat may still be attempted no matter how low effective skill drops.
Task Difficulty Scale
The GM may apply a task difficulty modifier to reflect how challenging or trivial a situation is, separate from personal modifiers for culture, equipment, or training. The full scale:
| Modifier | Difficulty | Driving Example |
|---|---|---|
| +10 | Automatic | Starting a car — GM should skip the roll entirely |
| +8 / +9 | Trivial | Empty parking lot — failure needs incredible bad luck |
| +6 / +7 | Very Easy | Empty suburban street |
| +4 / +5 | Easy | Commute to work in a small town |
| +2 / +3 | Very Favorable | Commute through a teeming metropolis |
| +1 | Favorable | Competing in a road rally |
| 0 | Average | Standard car chase — the benchmark |
| −1 | Unfavorable | High-speed car chase |
| −2 / −3 | Very Unfavorable | High-speed chase on a busy freeway |
| −4 / −5 | Hard | Chase while shooting a gun out the window |
| −6 / −7 | Very Hard | Chase during a blizzard |
| −8 / −9 | Dangerous | Chase + shooting + blizzard |
| −10 | Impossible | Steering with knees, firing a bazooka, in a blizzard |
Default Rolls
Most skills can be attempted untrained using a default roll — rolling against an attribute or related skill at a penalty. The skill description lists available defaults.
Lockpicking defaults to IQ−5. If Aldric has IQ 14, he can attempt to pick a lock by rolling against 14−5 = 9. A trained locksmith would roll against their Lockpicking skill instead — almost always better.
Some skills — like Alchemy, Karate, and all spells — have no default. You cannot attempt them without training.
Rule of 20: If a basic attribute exceeds 20, treat it as 20 when calculating defaults. So IQ 25 still gives a default Lockpicking of 15 (20−5), not 20. This cap does not apply to defaults from other skills.
Equipment Modifiers
The quality of tools affects rolls for skills that require equipment:
| Equipment Quality | Modifier | Cost |
|---|---|---|
| No equipment | −10 (tech) / −5 (other) | — |
| Improvised equipment | −5 (tech) / −2 (other) | — |
| Basic equipment | +0 | Standard price |
| Good quality | +1 | ~5× base price |
| Fine quality | +2 | ~20× base price |
| Best at your TL | +TL/2 (min +2) | Rarely for sale |
Time Modifiers
Working more carefully gives a bonus; rushing gives a penalty.
- Extra time: 2× as long = +1; 4× = +2; 8× = +3; 15× = +4; 30× = +5.
- Haste: −1 per 10% less time taken. Doing a task in half the usual time (−50%) = −5. Maximum reduction is normally 90% (one-tenth time) for −9.
All modifiers stack unless the rules say otherwise. Working in the dark (−9) with improvised tools (−2) at haste (−3) means your effective skill could drop 14 points below base.
Always tally modifiers before rolling — don't eyeball them mid-throw.
Major projects (build a bridge, write a book) use repeated daily rolls. Each worker rolls at end of day; success = 8 man-hours contributed; critical success = 50% extra; failure = half; critical failure = nothing, plus 2d hours of work destroyed!
A supervisor using Leadership or Administration instead of working personally can give the team +1 to +2 on success.
Degree of Success & Failure
A roll doesn't just succeed or fail — by how much matters. After determining the outcome, calculate the margin of success or margin of failure.
Effective skill 14, roll a 9: success. Margin of success = 14 − 9 = 5.
Effective skill 9, roll a 13: failure. Margin of failure = 13 − 9 = 4.
Many rules use these margins directly — a large margin of success often unlocks additional detail, speed, or quality of result. Large margins of failure mean worse consequences.
Critical Successes
A critical success is an especially good result. The GM determines the bonus — the lower the roll, the better.
| Roll | Critical Success if… |
|---|---|
| 3 or 4 | Always — regardless of effective skill |
| 5 | Effective skill is 15+ |
| 6 | Effective skill is 16+ |
In combat, a critical hit is a critical success on an attack roll — results come from the Critical Hit Table (Basic Set p. 556) rather than GM discretion.
Critical Failures
A critical failure is the worst possible outcome. The GM determines consequences — the higher the roll, the worse the result.
| Roll | Critical Failure if… |
|---|---|
| 18 | Always — regardless of effective skill |
| 17 | Effective skill is 15 or less; otherwise ordinary failure |
| Any roll | The roll is 10 or more above your effective skill (e.g., rolling 16 on a skill of 6) |
In combat, a critical miss uses the Critical Miss Table instead of GM discretion.
Repeated Attempts
The GM decides whether retry attempts are permitted based on the nature of the task:
- One chance only: Defusing a bomb, jumping a crevasse, vital surgery.
- Retry with damage: Assess damage and allow another attempt after a reasonable wait.
- Retry at penalty: Each additional attempt after a failure (with no damage) costs −1 cumulative: −1 on the second try, −2 on the third, and so on.
- Retry freely: Repeated attempts are the norm (e.g., attacking in combat, fishing).
In heroic or cinematic games, the GM may allow players to spend bonus character points to alter recent outcomes:
- 2 pts: Turn critical failure into ordinary failure
- 1 pt: Turn failure into success
- 2 pts: Turn success into critical success
Not recommended for horror or mystery games — it destroys suspense.
Contests
When two characters compete directly, each makes their own success roll. The result of comparing those rolls determines the winner. There are two contest types — choose based on how fast the competition resolves.
Quick Contests
A Quick Contest resolves in moments — two characters lunging for the same weapon, or arm-wrestling decided in a single test. Both competitors roll simultaneously:
| Outcome | Winner |
|---|---|
| One succeeds, one fails | The one who succeeded |
| Both succeed | The one with the larger margin of success |
| Both fail | The one with the smaller margin of failure |
| Tied margins | Nobody wins — stalemate, reroll, or each grabbed the weapon simultaneously |
The winner's margin of victory equals:
- If both succeeded: (winner's success margin) − (loser's success margin)
- If one succeeded, one failed: (winner's success margin) + (loser's failure margin)
- If both failed: (loser's failure margin) − (winner's failure margin)
Resistance Rolls are Quick Contests where one character is actively defending against an ability. Two special rules apply: (1) the attacker must succeed to win — a failure means the subject doesn't even need to roll; (2) all ties go to the defender.
The Rule of 16: When a supernatural attack (spell, psi ability, etc.) offers a resistance roll against a living or sapient target, the attacker's effective skill cannot exceed the higher of 16 or the defender's actual resistance score. A wizard with effective skill 18 rolling against a target with Will 12 still rolls against 16 — not 18.
Regular Contests
A Regular Contest is a drawn-out competition with back-and-forth — arm wrestling, a long chase, extended negotiations. Both characters roll each round:
- One succeeds, one fails: The one who succeeded wins the contest outright.
- Both succeed or both fail: No change — roll again. This continues until one succeeds while the other fails.
Each attempt represents an appropriate time interval — one second in a physical struggle, or potentially days in a library research race. The GM sets the time scale.
Extreme scores can bog down Regular Contests. If both contestants have skill 6 or less, temporarily raise both by enough to bring the lower to 10. If both have skill 14 or more, lower both to bring the lower to 10. This keeps dice rolling without distorting the relative advantage.
Quick Contest — Vora Disarms an Opponent
Caught in a tight corridor, Vora attempts to knock her opponent's sword aside — a Quick Contest of Broadsword skills.
Vora wins decisively. The opponent's weapon flies from their grip. The GM rules the large margin sends it skidding across the floor — out of easy reach.
Success Roll — Mira Scales a Wall
Mira scales a vertical stone wall (−3 to Climbing). She subtracts her encumbrance level (0 — she's travelling light), giving an effective skill of 12.
Mira succeeds with a margin of 3. The GM describes her finding solid handholds and pulling herself up steadily. The margin might earn her extra speed — she reaches the top in half the expected time.
Influence Roll — Aldric at the Gate
Aldric attempts to convince a suspicious gate guard to let the party through without inspection. He uses Diplomacy in a Quick Contest against the guard's Will.
Aldric wins. With Diplomacy, the GM also makes a regular reaction roll and takes the better of the two results. The guard waves them through — and the large margin of victory means he even apologises for the delay.
Physical Feats
For physical tasks not covered by a specific skill, use DX rolls for precision and HT rolls for endurance. The rules below cover the most common physical challenges in adventuring play.
Climbing
Roll against Climbing skill (defaults to DX−5) for anything harder than a ladder. Make one roll to start the climb and another every five minutes. Failure means you fall; critical failure means you fall even if roped unless the rope itself is secured.
Subtract your current encumbrance level (0–4) from every Climbing roll — carrying a heavy pack is dangerous on a rock face.
| Surface | Modifier | Combat Speed | Normal Speed |
|---|---|---|---|
| Ordinary tree | +5 | 1 ft/sec | 1 ft/3 sec |
| Ordinary mountain | 0 | 1 ft/2 sec | 10 ft/min |
| Vertical stone wall | −3 | 1 ft/5 sec | 4 ft/min |
| Modern building | −3 | 1 ft/10 sec | 2 ft/min |
| Rope (going up) | −2 | 1 ft/sec | 20 ft/min |
Jumping
The distance you can jump is based on Basic Move:
- High Jump (standing): (6 × Basic Move) − 10 inches. Running start: add yards run to Basic Move before calculating.
- Broad Jump (standing): (2 × Basic Move) − 3 feet. Running start: add yards run to Basic Move before calculating.
If you have Jumping skill, you may substitute half your skill level (rounded down) for Basic Move in these formulas. Roll against Jumping instead of DX for difficult jumps in combat.
Running & Sprinting
Normal ground movement is covered by your Move score. For sustained running over time:
- Sprinting: After one second of running, add 20% to your Move (round down; minimum +1). After every 15 seconds of sprinting, roll HT or Running skill — failure costs 1 FP.
- Paced running: Half sprinting speed, but FP loss rolls are every minute instead of every 15 seconds — you can go twice as far before exhaustion.
Swimming
Roll against Swimming skill (defaults to HT−4) whenever you enter water over your head. Failure means you inhale water and lose 1 FP; roll again in five seconds.
Human water Move = Basic Move ÷ 5 (rounded down, minimum 1). Apply encumbrance penalties normally — heavy armour at a river crossing is genuinely lethal.
Extra Effort
Through willpower alone, a character can push past normal physical limits. Roll against Will (or Will-based relevant skill) at −1 per 5% increase in desired capability. Success grants the increase; failure achieves nothing. Critical failure causes HP loss equal to the FP cost of the attempt.
Extra effort always costs 1 FP per attempt (or 1 FP per roll for ongoing tasks), whether you succeed or not.
Motivation matters. Characters who are afraid, angry, or protecting a loved one roll at +5 to extra effort — but typically require a Fright Check failure or a triggered disadvantage to qualify for the bonus. Desperation drives people past their limits.
Characters with the Machine meta-trait cannot use extra effort at all — they are limited by their hardware, not their will.
Sense Rolls
A sense roll is a success roll against your Perception (Per) score, modified by any relevant Acute Senses advantages. Vision, Hearing, and Taste/Smell are separate roll types. A successful sense roll tells you that you noticed something; a second roll against IQ (or an appropriate skill) may be needed to understand what you noticed.
If you have Danger Sense and fail a sense roll for something dangerous, the GM secretly rolls your Per again. On success, you sense the danger anyway — your subconscious picked up on something your conscious mind missed.
Vision
Make a Vision roll when it matters whether you see something. Modifiers include any Acute Vision bonus; size and range penalties (see Basic Set p. 550); and −1 to −9 for partial darkness. Total darkness makes Vision rolls impossible without special advantages. Spotting something obviously in your field of view (a car approaching on a road) gets +10; searching for hidden objects does not.
When trying to spot a deliberately hidden target, treat as a Quick Contest of your Perception vs. the concealer's Camouflage or Stealth skill.
Hearing
Make a Hearing roll when it matters whether you hear something. Modifiers include any Acute Hearing bonus and +4 for Discriminatory Hearing. The GM modifies for loudness and background noise. Trying to hear someone moving silently is a Quick Contest vs. their Stealth skill.
| Sound | Audible Range (no penalty) |
|---|---|
| Quiet conversation | ½ yard |
| Normal conversation | 1 yard |
| Loud conversation | 4 yards |
| Noisy office | 8 yards |
| Normal traffic | 16 yards |
| Heavy traffic | 64 yards |
| Jet takeoff | 128 yards |
Each step further than the listed range gives −1 to the roll; each step closer gives +1.
Taste & Smell
Make a Taste or Smell roll to notice a flavour or scent. Modifiers include any Acute Taste/Smell bonus and +4 for Discriminatory Smell or Taste. The GM modifies for intensity and disguise. Discriminatory Smell can identify people, locations, and objects with precision comparable to vision in a normal human — very useful for tracking.
Influence Rolls
An influence roll is a deliberate attempt to ensure a positive reaction from an NPC. It replaces the normal reaction roll (which is a simple 3d6 roll modified by the character's social traits — see Basic Set p. 494) when a player wants to actively work on an NPC rather than relying on passive impression.
How It Works
Choose which influence skill you are using: Diplomacy, Fast-Talk, Intimidation, Savoir-Faire, Sex Appeal, or Streetwise. Then roll a Quick Contest of your influence skill vs. the subject's Will.
| Outcome | Result |
|---|---|
| You win | NPC gives a "Good" reaction (or "Very Good" for Sex Appeal) |
| Any other outcome | NPC resents the attempt: "Bad" reaction (or "Very Bad" for failed Intimidation) |
Modifiers: Your reaction modifiers (appearance, social status, etc.) apply. Using an inappropriate skill for the situation gives −1 to −10 at the GM's discretion.
Diplomacy is a special case: on any outcome, the GM also makes a regular reaction roll, and takes the better of the two results. This makes Diplomacy the safest choice — even if you lose the Quick Contest, the normal reaction might still be favourable.
Special cases:
— Indomitable NPCs cannot be influenced at all unless you have an appropriate Empathy advantage.
— Unfazeable NPCs cannot be Intimidated.
— Slave Mentality NPCs automatically comply — no roll needed.
Influencing PCs
Influence rolls are designed for PCs influencing NPCs. When an NPC successfully uses an influence ability against a PC, the GM should apply the NPC's margin of victory as a bonus or penalty to relevant die rolls — not force the player to react in a specific way. For example, a beautiful spy who beats a PC's Will by 3 using Sex Appeal might impose −3 to that PC's Detect Lies rolls when dealing with her.
Will Rolls & Fright Checks
Will Rolls
When a character faces a stressful situation or distraction, the GM may call for a roll against Will. On success, the character acts normally. On failure, they submit to the distraction, fear, or pressure.
Will rolls ≠ self-control rolls. Which type of roll you make depends on the cause of the stress, not its effects. Environmental distraction → Will roll. Mental disadvantage triggered → self-control number. Modifiers for resisting a particular effect are generally interchangeable between both types, but the rolls themselves are not.
Fright Checks
A Fright Check is a Will roll made to resist fear. The GM calls for one only when an event is so unusual or terrifying it might stun or permanently scar the character — not for every dangerous moment. What qualifies as "ordinary" varies by genre and setting.
Fright Check Modifiers
| Condition | Modifier |
|---|---|
| Advantages / Disadvantages | |
| Each level of Fearlessness | +1 per level |
| Each level of Fearfulness | −1 per level |
| Combat Reflexes | +2 |
| Combat Paralysis | −2 |
| Unfazeable | No Fright Check needed at all |
| Circumstances | |
| In combat when the event occurs | +5 |
| Witnessed from 100+ yards away | +1 |
| Viewed remotely (camera, clairvoyance) | +3 |
| Alone | −2 |
| In the dark or at night | −1 |
| It physically touches you | −1 |
| Previous exposure to this specific threat (same 24 hrs) | +1 per exposure |
| The Rule of 14 | |
| If modified Will exceeds 13… | Treat as 13 for Fright Checks only |
The Rule of 14 is unique to Fright Checks. No matter how high your Will, the maximum target number for a Fright Check is 13. A roll of 14 or higher automatically fails. Even the bravest hero can be rattled by something truly horrifying.
Fright Check Results
When you fail a Fright Check, roll 3d6 and add your margin of failure to the result, then consult the table. The GM may adjust implausible results.
| Total | Effect |
|---|---|
| 4–5 | Stunned for 1 second; recover automatically. |
| 6–7 | Stunned for 1 second; roll vs. Will each second to recover. |
| 8–9 | Stunned for 1 second; roll vs. modified Will each second to recover. |
| 10 | Stunned for 1d seconds; roll vs. modified Will each second to recover. |
| 11 | Stunned for 2d seconds; same recovery. |
| 12 | Retching for (25−HT) seconds; roll vs. HT each second to recover. |
| 13 | Acquire a new Mental Quirk. |
| 14–15 | Lose 1d FP and stunned for 1d seconds. |
| 16 | Stunned for 1d seconds and acquire a new quirk. |
| 17 | Faint for 1d minutes; roll vs. HT each minute to recover. |
| 18 | Faint; roll vs. HT — failure means 1 HP of injury as you collapse. |
| 20 | Faint for 4d minutes; lose 1d FP. |
| 21 | Panic — useless for 1d minutes; roll vs. Will to snap out of it. |
| 22 | Acquire a −10-point Delusion. |
| 23 | Acquire a −10-point Phobia or mental disadvantage. |
| 28–29 | Coma — roll vs. HT every 30 min (light) or every hour (full coma) to recover. |
| 30 | Catatonia for 1d days; progressive HP loss without medical care. |
| 40+ | As above, plus lose 1 point of IQ permanently. |
New traits acquired from Fright Check results must be related to the terrifying event, and ideally to the character's existing mental traits. They reduce the character's point total. The GM assigns them — players do not choose.