Bet On It


by Keith MacKenzie

British secret agents in casinos, American secret agents at horse tracks, gunslingers in saloon card games. Gambling has an air of mystery about it and many players have given their characters skill in this area. These rules, presented for GURPS Fourth Edition, allow the skill to mean something beyond flavor text. They do not encompass cliché things such as betting everything on one roll of the dice or betting on one's favorite team no matter how poor they play. While the first is a gambit, neither is gambling. Gambling is playing a series of games with the intention of coming out ahead.

Lottery Games

Lottery games are games where gambling skill does not apply. This would include Roulette, Bingo, and the ever popular slot machines. For each hour of gambling, the character determines how much he is willing to lose. With the stake determined, the player then rolls against a 10. The margin of success times 10% of the stake is the profit (the stake is not lost). If the roll failed, the character loses 10% of the stake per point of failure. On a critical failure, the character loses their entire stake, and must make a Will roll. If the Will roll is successful, no further losses occur this hour. If the roll fails, the character loses all currency with him and on a critical failure will lose anything else of value with them, such as jewelry, vehicles, or weapons, if the venue will take them in trade (the charactergets no cash value, but some establishments will not accept anything besides cash).

House Games

House games are games where skill comes into play, and the house wins or loses to each player separately. Examples include Blackjack, Craps, Horse Racing, Sports Book, and Video Poker. If the game has a dealer, the dealer will always be the house. The house may have a stake maximum and most tables will have a minimum (usually 10 times the minimum bet, so a $5 table would require a $60 stake). As with Lottery games, each player decides his stake for that hour and rolls against his Gambling skill. The House rolls against 14. The player's margin of success minus the house's margin of success times 10% of the player's stake is how much the player wins or loses. The stake is still kept. If the player loses more than 100% of his stake, a Will roll must be made. If it succeeds, only the stake is lost. If the roll fails, all currency the player has is lost; on a critical failure, other items of value are also lost. Sports Book and horse racing may use appropriate skills instead of gambling if they have actual recent experience with all the competitors.

Casino Option: If a player stake is more than the cost of a room, and the player scores a critical success, his room will be free (comped). If a player gets two critical successes in a row or four in an evening, the dealer will be replaced with a ringer (House skill becomes 16) or a cooler might be sent (cancels luck advantage for one hour). If a player gets three critical successes a row or 6 in one night or more than 10 in a week, the gambler will be shown out of the casino and may be beaten. Note that it is better for High skill gamblers to play zero-sum games.

Racing and Sport Book

This is gambling on athletic competition. It is essentially treated as house games except that players may use other appropriate skills, if they can show that a skill is applicable. A gambler who has Riding and has visited the stables and seen all the horses personally could use that skill instead of Gambling. A sports fan with sufficient study of recent games and Strategy: Football could use that skill.

Zero-Sum Games

Zero-Sum games are games where players win or lose among themselves. The house gets nothing (although in many games the house gets an entrance fee). The stake may be set ahead and each player starts with the same amount of money, or may be open to whatever people bring. Poker is the most common game for this sort of gambling, but other games do exist. Billiards also falls into this category, except Hobby: Billiards is used instead of gambling.

If the game has a fixed stake, each player wagers that amount each hour. Each player rolls against his Gambling skill. The margins of success and failure are averaged, and this number is subtracted from the margin of each player. Each player then wins or loses 10% times his adjusted margin of the stake. When a player does not have enough to cover his loss, the players who lose will pay their losses first and then pay extra until all the winners are paid. The winners are paid off in margin order.

Example: Adam, Bennie, Carlos, and Dieter gather for their weekly $100 stake game. Their skills are all 12. For the first hour their rolls are 5, 10, 11, and 7. Their margins of success are 7, 2, 1, and 5 which average 3.75. Adam wins 7 (his margin of success) ­ 3.75 (average margin of success) × 10% × $100 = $32.50. Bennie loses $17.50, Carlos loses $27.50, and Dieter wins $12.50. They now have $132.50, $82.50, $72.50, and $112.50 respectively.

The next hour the stakes are still $100, and the rolls are 8, 17, 12, and 8. The margins of success are 4, -5, 0, and 4 averaging .75. Adam and Dieter each win $32.50, Carlos loses $7.50, and Bennie loses $57.50. After two hours their individual totals are $165, $25, 65, and $145.

It's now Hour Three, and the rolls are 7, 16, 13, and 6. The margins are 5, -4, -1, and 6, averaging 1.5. Because Bennie will not have enough to cover his loss of $55, Dieter will collect his $45 first. Carlos loses $25 for his roll, and $25 comes from Bennie's remaining stake, providing Dieter's $45. This leaves $5 left over for Adam who still has $35 coming; Adam's remaining $30 will be paid by Carlos, because he had the next smallest margin of success. At the end of hour three, Adam has $205, Bennie has nothing, Carlos has $5, and Dieter has $190. If Carlos did not have enough, then Adam would have had to make up the difference, but it would have been to himself.

In a variable stake game, the players with larger stakes will essentially play more hands. Each player's stake is divided by the smallest stake and the player will make that many rolls. Each roll is resolved independently, in the same manner as fixed stake games. If Ernie is staking $20, Fred is staking 100, and Gregory stakes 60, Ernie will make 1 roll, Fred will make 5 and Gregory will make 3. All nine rolls will be normalized and the payoffs will be relative to Ernie's $20 stake.


Players may cheat if they wish. They should roll each hour before their skill roll against Sleight of Hand (or whatever skill they are using) at -1 per point of Gambling skill adjustment. The cheater may adjust his own skill or another player's, and the adjustment may be made up or down. Other players and the house will roll against perception with a bonus of the same amount. The House has Per 14 at TL5, 16 at TL6, 20 at TL7, and 30 at TL8. The house will also use methods to catch magic or psionics if those things are common in the world. If a cheater is caught, the repercussions range from being thrown out to being killed. If a cheater is raising another player's skill, that player will suffer the same fate. If another player's skill was being lowered, that player will be encouraged by the house to call it a night and his room comped.

Gamblers may wish to pull their punch, or play at a lesser level, either to avoid too many critical successes at table games, as part of an elaborate set-up, or just a hustle. A character pulling his punch must make an Acting ­ (¼the skill reduction) roll, or the other players or the house will know the player is more skilled than he seems. Critical success and failure are calculated from the played at skill.


Article publication date: December 23, 2005

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