Remove the Margin
Enter home, draw and away odds and compare proportional, additive, power and Shin fair probabilities side by side.
Lab 2 · Remove the margin
Synthetic · deterministicEnter a complete home / draw / away market. The lab removes the bookmaker margin four ways.
Book sum104.81%
Overround4.81%
Theoretical payout95.41%
Largest method gap0.58 pts
| Method | Home | Draw | Away |
|---|---|---|---|
| Raw implied (with margin) | 47.62% | 29.41% | 27.78% |
| Proportional | 45.43% (2.201) | 28.06% (3.563) | 26.50% (3.773) |
| Additive | 46.02% (2.173) | 27.81% (3.596) | 26.17% (3.820) |
| Power k = 1.0461 | 46.02% (2.173) | 27.80% (3.597) | 26.18% (3.819) |
| Shin z = 0.0241 | 45.87% (2.180) | 27.87% (3.588) | 26.26% (3.808) |
- Proportional: Divides every implied probability by the book sum. Simple, but assumes the margin is spread in proportion to probability.
- Additive: Removes an equal amount from every outcome. Easy to explain; it can push long shots below zero.
- Power: Raises every implied probability to a common power. Takes relatively more margin from long shots.
- Shin: Derived from Shin's insider-trading model. Takes more margin from long shots; performed well in Štrumbelj (2014).
Reading the result. The methods agree on the favourite more than on long shots. None of them recovers the “true” probability: they are different assumptions about how the bookmaker spread its margin. Differences of a point or two can decide whether a price looks like value, so state which method you used.
Educational calculator. Uses only the numbers you enter or seeded synthetic data — no live prices, no staking, no real money.