Understanding probability is what separates good backgammon players from great ones. Every decision in backgammon involves risk, and knowing the actual odds helps you make better choices at every point in the game.
Key Takeaways
- There are exactly 36 possible dice combinations; 7 is the most common total (probability: 16.67%)
- Doubles occur once every 6 rolls on average (16.67% of the time)
- A blot 1 pip away from a single opponent checker has a 30.6% chance of being hit
- No checker can be directly hit by a single checker more than 11 pips away (7+4 or 6+5 max)
- The starting pip count for each player is 167; the player with the lower pip count leads the race
- Knowing your "cubeless equity" — your winning probability without cube leverage — drives all major decisions
Dice Probability Fundamentals
With two six-sided dice, there are 36 possible combinations (6 × 6). However, since the order of dice matters in probability but not in play, some totals are more likely than others.
Probability of Each Total
| Total | Combinations | Probability | Ways to Roll |
|---|---|---|---|
| 2 | 1 | 2.78% | 1-1 |
| 3 | 2 | 5.56% | 1-2, 2-1 |
| 4 | 3 | 8.33% | 1-3, 3-1, 2-2 |
| 5 | 4 | 11.11% | 1-4, 4-1, 2-3, 3-2 |
| 6 | 5 | 13.89% | 1-5, 5-1, 2-4, 4-2, 3-3 |
| 7 | 6 | 16.67% | 1-6, 6-1, 2-5, 5-2, 3-4, 4-3 |
| 8 | 5 | 13.89% | 2-6, 6-2, 3-5, 5-3, 4-4 |
| 9 | 4 | 11.11% | 3-6, 6-3, 4-5, 5-4 |
| 10 | 3 | 8.33% | 4-6, 6-4, 5-5 |
| 11 | 2 | 5.56% | 5-6, 6-5 |
| 12 | 1 | 2.78% | 6-6 |
Key insight: 7 is the most likely total, and extreme values (2, 12) are rare.
Probability of Doubles
The chance of rolling any specific double: 1/36 = 2.78%
The chance of rolling any double at all: 6/36 = 16.67%
Doubles happen about once every 6 rolls.
Hitting Probabilities
One of the most important probability tables in backgammon is the chance of being hit based on distance. This assumes a single opposing checker can reach your blot:
Direct Hitting Chances (One Checker)
| Distance | Out of 36 | Probability |
|---|---|---|
| 1 | 11 | 30.6% |
| 2 | 12 | 33.3% |
| 3 | 14 | 38.9% |
| 4 | 15 | 41.7% |
| 5 | 15 | 41.7% |
| 6 | 17 | 47.2% |
| 7 | 6 | 16.7% |
| 8 | 6 | 16.7% |
| 9 | 5 | 13.9% |
| 10 | 3 | 8.3% |
| 11 | 2 | 5.6% |
| 12 | 3 | 8.3% |
| 15 | 1 | 2.8% |
| 16 | 1 | 2.8% |
| 18 | 1 | 2.8% |
| 20 | 1 | 2.8% |
| 24 | 1 | 2.8% |
Key insights:
- 6 or fewer points away = direct hit range (30-47% chance)
- 7+ points away = indirect hit only (needs combination or doubles)
- Distance of 7 is a major safety threshold — hitting chance drops from ~47% to ~17%
The Rule of Eights
A quick mental shortcut: Count the number of “shots” (dice combinations that hit) and multiply by 3 to get a rough percentage. For more precision, divide by 36.
Entering from the Bar
When you have a checker on the bar, your ability to enter depends on how many points in your opponent’s home board are open:
| Open Points | Chance to Enter | Chance to Stay on Bar |
|---|---|---|
| 6 (all open) | 100% | 0% |
| 5 | 97.2% | 2.78% |
| 4 | 88.9% | 11.1% |
| 3 | 75.0% | 25.0% |
| 2 | 55.6% | 44.4% |
| 1 | 30.6% | 69.4% |
| 0 (closed board) | 0% | 100% |
Key insight: With only 2 open points, you’ll fail to enter nearly half the time. A closed board is absolute — no entry is possible.
Bearing Off Probabilities
Bearing Off in One Roll
From various positions in the home board, the probability of bearing off all remaining checkers in exactly one roll:
2 checkers remaining:
- Both on the 1-point: 100%
- 1-point and 2-point: 100%
- Both on 6-point: 17/36 = 47.2%
The last two checkers: The probability of bearing off your last 2 checkers in one roll varies dramatically based on their positions. High point numbers require specific high rolls.
Pip Count and Race Probability
In a pure race, the relationship between pip count and winning probability is approximately:
- Equal pip count: ~50% each
- Leading by 5 pips (at 80 total): ~58%
- Leading by 10 pips (at 80 total): ~66%
- Leading by 15 pips (at 80 total): ~73%
- Leading by 20 pips (at 80 total): ~80%
The value of each pip depends on the total distance remaining. A 5-pip lead at 80 total pips is more significant than a 5-pip lead at 150 total pips.
Practical Applications
Should You Leave a Blot?
When deciding whether to leave a blot:
- Count the number of rolls that hit you
- Divide by 36 to get the probability
- Consider what happens if you’re hit vs. not hit
- Compare with the expected value of safer alternatives
Slotting Decisions
Slotting (placing a single checker to build a point) is worthwhile when:
- The probability of being hit is low
- The value of making the point is high
- You have good timing to cover the blot next turn
Double/Take Decisions
Probability directly drives cube decisions:
- Know your approximate winning percentage
- Compare against the 75%/25% thresholds (money play)
- Factor in gammon probability
Frequently Asked Questions
What are the odds of rolling a specific number in backgammon?
With two dice, the probability of rolling at least one specific number (e.g., a 3 on either die) is 11/36 ≈ 30.6%. For any exact total (like exactly 7), it depends on how many combinations produce that total — 7 has 6 combinations out of 36 (16.67%).
How often do doubles occur in backgammon?
Doubles occur 6 times out of 36 possible combinations — a probability of 16.67%, or roughly once every 6 rolls.
What is the probability of being hit when leaving a blot?
It depends on how far the opponent’s checker is from your blot. A blot 1 pip away from one opponent checker faces an 11/36 (30.6%) chance of being hit. A blot 7 pips away faces a 6/36 (16.7%) chance. Blots more than 11 pips away cannot be directly hit by a single checker.
What does “equity” mean in backgammon?
Equity is a measure of a position’s value, typically expressed as the expected outcome from −1 (certain loss) to +1 (certain win) in money game, or in terms of expected match points. Equity-based thinking — making the move that maximizes expected outcome — is the foundation of computer-era backgammon.
What is the starting pip count in backgammon?
Both players begin with a pip count of exactly 167. This is the total distance all 15 checkers must travel to bear off from the standard starting position.
Further Reading
- Strategy Guide — Apply probability to strategy
- Doubling Cube — Probability-driven cube decisions
- Pip Count Guide — Race probability in practice
- Backgammon Dice — All 36 combinations and their probabilities
- Opening Moves — Mathematically optimal openings