Game & Slam Odds at IMPs
How good must your contract be before bidding it? Break-even percentages computed from real scores and the official IMP scale.
Decision
Vulnerability
Break-even chance of making
37.5%
If the tricks are there (10)
4♠︎: +620 · 3♠︎: +170 -> +10 IMP
If they are not (9)
4♠︎: −100 · 3♠︎: +140 -> -6 IMP
Bid it whenever you judge the chance of making above 37.5%. Below that, stopping lower scores better in the long run.
At matchpoints the math is different: frequency beats size, so most close decisions hinge on 50%, not on these numbers.
All break-even percentages
| Decision | Not vul | Vul |
|---|---|---|
| Major game (4M vs 3M) | 45.5% | 37.5% |
| 3NT vs 2NT | 45.5% | 37.5% |
| Minor game (5m vs 4m) | 45.5% | 37.5% |
| Small slam (6M vs 4M) | 50.0% | 50.0% |
| Small slam (6NT vs 3NT) | 50.0% | 50.0% |
| Grand slam (7M vs 6M) | 56.0% | 56.7% |
| Grand slam (7NT vs 6NT) | 56.0% | 56.7% |
Judge it at the table
Bidding puzzles score your decisions against every possible layout, so you learn when the odds are really there.
Try bidding puzzlesFAQ
When should I bid a vulnerable game at IMPs?
A vulnerable major-suit game needs only about a 37.5% chance of making to be a good bet at IMPs: you risk 6 IMPs to gain 10.
What odds does a small slam need?
Roughly 50%. The IMP gain for bidding a making slam is about the same as the loss when it goes down, vulnerable or not.
What odds does a grand slam need?
Better than 50%: you risk the whole small-slam score to gain the grand-slam bonus, so you need about 55-56% at IMPs.