IMP Scoring Explained

IMPs (International Match Points) are the currency of team bridge. While matchpoint pairs games compare you to everyone in the room, IMP team games put your foursome against another foursome in a direct showdown. Two tables, same boards, opposite perspectives. Whoever gets the better result on each board wins IMPs.

The scoring system changes everything about how you bid and play.

The Basic Concept

You and your partner sit North-South at Table 1. Your teammates sit East-West at Table 2. Both tables play Board 5. At your table, you bid 4♥ and make it for +420. At the other table, your teammates defend against 4♥ and the opponents make it for -420 from your team’s perspective.

Net result: 0. You won 420 at your table, they lost 420 at their table. The board is a push. No IMPs to either team.

Now imagine a different scenario. You bid and make 4♥ for +420. At the other table, your teammates defend against 3♥ and it makes exactly for -140.

Net result: +420 - 140 = +280 for your team. But you don’t win 280 IMPs. You win 7 IMPs according to the conversion table.

The IMP Scale

The IMP conversion table takes the point difference between tables and converts it to IMPs. The scale is designed so small differences are small swings, medium differences are medium swings, and big differences are large swings, but not proportionally large.

Here’s the table (you don’t need to memorize this, scoring programs do it automatically):

The key insight: the scale is logarithmic. Losing 50 points costs you 2 IMPs. Losing 500 points costs you 11 IMPs. That’s 10 times the points but only 5.5 times the IMPs.

This dampens the impact of disasters. Yes, going down in a cold slam hurts. But it won’t single-handedly lose you the match. You can recover.

Common IMP Swings

Let’s look at typical scenarios and what they cost in IMPs.

Overtrick differences: You make 4♠ with an overtrick (+450), they make it exactly (+420). Difference: 30 points = 1 IMP.

Partscore vs game: You stop in 2♠ making 4 (+170), they bid 4♠ making (+420). Difference: 250 points = 6 IMPs.

Game vs slam: You make 4♥ (+420), they bid and make 6♥ (+980). Difference: 560 points = 11 IMPs. Ouch.

Down in game: You go down one in 4♠ (-50), they stop in 3♠ making 4 (+170). Difference: 220 points = 6 IMPs.

Slam disaster: You go down in 6♥ (-50), they make 4♥ (+420). Difference: 470 points = 10 IMPs. Painful but not catastrophic.

Why IMPs Change Strategy

In matchpoints, overtricks are gold. The difference between +420 and +450 can move you from an average board to a top. In IMPs, that same 30-point difference is worth 1 IMP. Not nothing, but not worth risking your contract.

Look at a typical decision. You’re in 3NT and can play safe for 9 tricks, or risk it for a possible 10th trick with a finesse. In matchpoints, you take the finesse every time. The field is in 3NT, and if you make 10 tricks while they make 9, you beat them all.

In IMPs, you play safe. If the finesse loses and you go down, you lose 10 IMPs (the difference between +400 and -50 is about 450 points). If the finesse works, you gain 1 IMP (the difference between +400 and +430). Risk 10 IMPs to gain 1 IMP? No thanks.

This principle applies everywhere. In IMPs:

• Making contracts is more important than overtricks
• Bidding sound games is more important than pushing for thin games
• Not going down in close slams matters more than missing them
• Defensive accuracy matters more than creating swing boards

The 50-50 Rule

Here’s a useful guideline for slam bidding in IMPs. If a slam is better than 50% to make, you should bid it. Worse than 50%, you shouldn’t.

Why? Let’s say you’re looking at a small slam that makes about 60% of the time. If you bid it:

• 60% of the time you make it and gain 11 IMPs (difference between slam and game)
• 40% of the time you go down and lose 10 IMPs

Expected value: (0.60 × 11) - (0.40 × 10) = 6.6 - 4.0 = +2.6 IMPs on average. Good bid.

Now look at a 45% slam:

• 45% of the time you make it and gain 11 IMPs
• 55% of the time you fail and lose 10 IMPs

Expected value: (0.45 × 11) - (0.55 × 10) = 4.95 - 5.5 = -0.55 IMPs on average. Bad bid.

The crossover is right around 50%. In matchpoints, you bid slams that are 35-40% to make, because if they make you get a top and if they fail you still beat pairs who didn’t bid game. In IMPs, you need better odds.

Vulnerable vs Not Vulnerable

Vulnerability changes the numbers but not the principles. When you’re vulnerable, going down costs more. Going down one vulnerable is -100 instead of -50. This means the IMP swings are bigger.

Vulnerable game making is +620 instead of +420 (200-point difference = 5 IMPs). Vulnerable slam making is +1430 instead of +980 (450-point difference = 10 IMPs).

The strategic effect is subtle. Vulnerable, you should be slightly more conservative in bidding because the penalty for failure is higher. Not vulnerable, you can be slightly more aggressive because going down is cheaper. But the 50-50 rule still basically applies.

Partscore Decisions

One of the trickiest IMP decisions is whether to compete to the three-level in a partscore battle. The opponents bid 2♥, you compete to 3♣. Should you?

The math depends on several factors:

• If 3♣ makes and 2♥ makes, you gain about 3-4 IMPs
• If 3♣ goes down and 2♥ makes, you lose about 5-6 IMPs
• If 3♣ goes down but 2♥ also fails, you might lose or gain depending on exact scores

In general, if you’re about 50% to make 3♣ and you think 2♥ makes, it’s close. Many experts err on the side of bidding because if the other table also competes to 3♣, you push the board. But if you’re the only table bidding 3♣ and you go down, it costs.

Defensive Decisions

In matchpoints, you might make a risky lead to try for a top. In IMPs, you make the percentage lead that gives your side the best chance to beat the contract.

Here’s an example. The opponents are in 3NT and you’re on lead with ♠KQJ95. You also have ♣AQ4. Do you lead your spade sequence or try the club queen?

In matchpoints, if the club queen finds partner with the king, you might beat 3NT when everyone else lets it make. Top board. Worth the risk.

In IMPs, you lead the spade. The club lead might work, but it might also give away a trick and turn a plus score into a minus. The safe lead gives you the best chance to beat the contract, and that’s what matters.

Scoring in Team Matches

Most team matches are scored across multiple boards. A typical match might be 16 boards. At the end, you add up all the IMPs from each board. If you’re up 30 IMPs, you win. If you’re down, you lose.

Some events convert the IMP difference to Victory Points (VPs), which standardize results across different matches. The details vary by event, but the concept is that winning by 20 IMPs gives you more VPs than winning by 5 IMPs, but not four times as many. Again, logarithmic scale.

For Swiss team events, VPs determine your ranking and who you play in the next round.

Strategy Differences From Matchpoints

To summarize the key strategic differences:

Bidding: Sound games and slams in IMPs. Aggressive thin games in matchpoints.

Declarer play: Protect your contract in IMPs. Go for overtricks in matchpoints.

Defense: Percentage defense in IMPs. Try to beat your specific contract. In matchpoints, consider the layout that gives you a top.

Competitiveness: In IMPs, let them play bad contracts. In matchpoints, compete to push them higher even if you go down.

Risk: In IMPs, avoid unnecessary risks. The reward for success is small compared to the cost of failure. In matchpoints, every board matters equally, so calculated risks pay off.

Why Teams Use IMPs

The IMP scale makes team bridge more about skill and less about luck. If you bid a terrible slam on one board, you lose 10 IMPs. But if you make 10 good decisions on other boards, you can make up those 10 IMPs. One disaster doesn’t end your match.

Compare that to matchpoints, where one bottom board is hard to recover from. In IMPs, you can lose a board badly and still win the match. This rewards consistent good judgment over the course of 16 or 20 or 32 boards.

It also makes the game more strategic. You’re not trying to beat the field on every board. You’re trying to make the highest-percentage decisions that will give your team the best chance to win IMPs over the course of the match.

For most serious players, team games feel more like “real bridge” than matchpoint pairs. The scoring system aligns better with good decision-making. And when you win a close team match by 3 IMPs, you know every decision mattered.