Introduction
The GURPS System
What the game is, how the system works, and the three fundamental mechanics you'll use every time you play.
What Is GURPS?
GURPS stands for Generic Universal RolePlaying System — originally a working code name that stuck. Now in its Fourth Edition, the name is more appropriate than ever. Each word is a design principle, not just a label.
GURPS uses plain English units throughout — distances in feet and miles, times in minutes and seconds. This makes it straightforward to import material from other games or supplements. If you see an interesting adventure for a different system, you can translate it directly.
What Is Roleplaying?
In a roleplaying game, each player takes the part of a character participating in a fictional adventure. A referee — the Game Master (GM) — sets the scene, controls the world, and plays the non-player characters the party meets. The GM describes what characters see and hear; players describe what they do in response; the GM describes the consequences. And so on.
Roleplaying is not purely competitive. The party usually succeeds or fails as a group. It is also one of the most creative forms of entertainment: unlike passive media, the audience is the story. The GM provides the raw material, but the final shape comes from the players themselves.
The GM determines outcomes in three ways: arbitrarily (for the best story), by specific rules (to determine what is realistically possible), or by rolling dice (for interesting random results). Knowing when to use each is the heart of good GMing.
The Three Game Mechanics
The entire GURPS system rests on three types of die rolls. Everything else — combat, social interaction, exploration, magic — is built on top of these. Learn these three, and you can begin playing immediately.
The character creation system is a fourth important element, but you do not need it during play — all the relevant calculations are done beforehand and recorded on your character sheet.
Success Rolls
A success roll is the most common roll in GURPS. Any time a character attempts something with a meaningful chance of failure, the player rolls 3d (three six-sided dice) and compares the total to a target number — usually a skill level or attribute.
Roll 3d > target number → FAILURE
Roll 17 or 18 → AUTOMATIC FAILURE (no matter how high the target)
Roll 3 or 4 → CRITICAL SUCCESS (no matter what)
Modifiers
The GM applies modifiers to the target number based on how hard the task is. A harder task lowers the effective target; an easier one raises it. These are written as Skill±N.
Your ST is 12. Normally you'd roll against ST 12. But the door is very heavy — the GM calls for ST−2. Your effective target drops to 10. You must roll 10 or less on 3d to succeed.
Your Animal Handling is 12. The dog is unusually friendly, so the GM gives +4. Your effective target is 16. Rolling 16 or less on 3d succeeds — easy task, high probability of success.
Base Skill vs. Effective Skill
Your printed skill level is your base skill — your odds under average adventuring conditions. After all modifiers are applied, the final number you roll against is your effective skill. In low-stakes situations, the GM may add +4 or more — or simply rule that success is automatic.
Rolling 17 or 18 always fails, so base skill above 16 doesn't improve normal success odds. The value of high skill is in absorbing penalties. A difficult lock gives −6. With Lockpicking-15, you're left at effective skill 9. With Lockpicking-23, you're still at 17 — still near-certain success.
Reaction Rolls
When the player characters meet an NPC and the GM wants to determine how that NPC feels about them, he rolls 3d and consults the Reaction Table. The higher the roll, the more favorably the NPC reacts.
This roll is always optional. The GM may predetermine reactions for story reasons — reaction rolls exist to add unpredictability and to make character traits feel consequential.
Many traits provide reaction modifiers. If your character has a +2 reaction bonus from Appearance, the GM adds 2 to every reaction roll made by someone who can see you. Disadvantages like Odious Personal Habits impose negative modifiers. These modifiers are noted on your character sheet and applied automatically.
Damage Rolls
When a character successfully hits in combat, a damage roll determines how much harm was done. Damage rolls use the dice+adds notation described in Conventions below.
Several things modify final injury: armor reduces damage received, some attacks do extra damage after penetrating armor, and critical hits can dramatically increase results. The combat system is modular — you can use just the core rules for a fast game, or add optional layers for detail and realism.
A weapon does 2d+3 damage. Roll 2 dice and add 3. Roll a 7 → total damage is 10. If the target's armor absorbs 4 points, the final injury is 6 hit points.
Mini-Glossary
These are the core terms used throughout both volumes. A complete glossary appears at the back of the book. The definitions here are enough to understand the Quick-Start rules without flipping pages.
| Term | Definition | See Also |
|---|---|---|
| advantage | A useful trait that gives you an "edge" over someone with comparable attributes and skills. | Chapter 2 |
| attributes | The four core numbers — ST, DX, IQ, HT — that rate a character's most basic abilities. Higher is always better. | pp. 14–15 |
| cinematic | A style of play where story needs outweigh realism, even when that produces improbable results. | p. 488 |
| d | Short for "dice." "Roll 3d" means roll three ordinary six-sided dice and add them up. | Conventions, below |
| Dexterity (DX) | Attribute measuring agility and coordination. Controls most physical and combat skills. | p. 15 |
| disadvantage | A problem that renders you less capable — but returns points for you to spend elsewhere. | Chapter 3 |
| enhancement | An extra capability added to a trait. Increases its point cost by a percentage. | pp. 102–109 |
| Fatigue Points (FP) | Measures resistance to exhaustion from physical exertion, casting spells, and similar effort. | p. 16 |
| Health (HT) | Attribute measuring physical grit, vitality, and resistance to disease and injury. | p. 15 |
| Hit Points (HP) | Measures ability to absorb physical damage before falling unconscious or dying. | p. 16 |
| Intelligence (IQ) | Attribute measuring brainpower, common sense, and creativity. Controls most mental and social skills. | p. 15 |
| limitation | A restriction on the use of a trait. Reduces its point cost by a percentage. | pp. 110–117 |
| point | The currency of character creation. Spent to buy traits. Written in brackets — e.g., Combat Reflexes [15] costs 15 points. | p. 10 |
| prerequisite | A trait you must already have before learning another. For skills, you need at least 1 point in it. | p. 169 |
| skill | A number defining your trained ability in an area of knowledge or class of tasks. | Chapter 4 |
| Strength (ST) | Attribute measuring physical muscle and bulk. Determines basic damage and carrying capacity. | p. 14 |
| trait | Any advantage, attribute, disadvantage, skill, or other character building block that affects play and costs points. | Throughout |
Dice Conventions
GURPS uses six-sided dice only. Every success roll uses exactly three dice. Damage and other variable quantities use the dice+adds notation.
| Notation | Meaning | Example Result |
|---|---|---|
| 3d | Roll three six-sided dice, add the results. Used for all success rolls. | Range: 3–18 |
| 4d+2 | Roll four dice, add 2 to the total. Standard dice+adds format. | Range: 6–26 |
| 3d−3 | Roll three dice, subtract 3 from the total. Result can reach 0 or below. | Range: 0–15 |
| 2d×10 | Roll two dice and multiply the result by 10. Used for very large numbers. | Range: 20–120 |
| 5d | Roll five dice and add. Can appear in encounter tables or large damage values. | Range: 5–30 |
A weapon does 2d+4 cutting damage. Roll 2 dice: say you get a 3 and a 5, total 8. Add 4: the attack does 12 points of cutting damage before armor is applied.
An adventure reads: "The base holds 5d soldiers and 2d+1 robots." Roll 5 dice for the soldiers, then roll 2 dice and add 1 for the robots. Every run of this encounter will be different.
Rounding Rules
Math in GURPS often produces fractions. Two different rounding rules apply depending on context — and getting them right matters for point costs.
| Context | Rule | Example |
|---|---|---|
| Point costs | Round up (fractions become the next whole number). For negative costs, "up" means toward zero. | 25% enhancement on 15-pt trait → 18.75 → 19 pts −7 pts × ½ = −3.5 → −3 pts |
| Character feats & combat | Round down (drop the fraction). Applies to lifting, jumping, damage, and all physical results. | 3 injury + 50% bonus = 4.5 → 4 pts of injury |
When a specific rule rounds differently — to the nearest whole number, or not at all — it says so explicitly in the text. If no instruction is given, use the two rules above based on whether you're calculating a cost or a result.
Metric Conversions
GURPS uses imperial units (feet, miles, pounds). The table below provides both a quick gaming approximation and the precise real-world metric equivalent.
| Imperial | Game Metric (approx.) | Real Metric (exact) |
|---|---|---|
| 1 inch | 2.5 cm | 2.54 cm |
| 1 foot | 30 cm | 30.48 cm |
| 1 yard | 1 meter | 0.914 m |
| 1 mile | 1.5 km | 1.609 km |
| 1 pound | 0.5 kg | 0.454 kg |
| 1 ton | 1 metric ton | 0.907 metric tons |
| 1 gallon | 4 liters | 3.785 liters |
| 1 quart | 1 liter | 0.946 liters |
| 1 ounce | 30 grams | 28.349 grams |
| 1 cubic inch | 16 cubic cm | 16.387 cu. cm |
| 1 cubic yard | 0.75 cubic m | 0.765 cubic m |
One degree Fahrenheit = 5/9 of one degree Celsius. To convert a thermometer reading: subtract 32 from the °F value, then multiply by 5/9. So 95°F → (95−32) × 5/9 = 63 × 5/9 = 35°C.
The "Game Metric" column is designed for fast mental conversion at the table. If a range is 30 yards, call it 30 meters. If a character carries 200 lbs., call it 100 kg. The rounding introduces minimal error and keeps the game moving.