The margin in one sentence
The margin is the share of the money staked that the operator keeps over time. You can see it when you add up the implied probabilities (1 ÷ odds) of every outcome in a market: the total is always above 100%.
The calculation
- For each outcome, divide 1 by the odds.
- Add up the results. We call this sum S.
- Work out the margin in one of two ways:
- Overround (the excess above 100%): S − 1.
- Share of total stakes (the part of every euro staked that the operator keeps): (S − 1) ÷ S.
Example with odds of 1.85 / 3.60 / 4.20:
- S = 0.5405 + 0.2778 + 0.2381 = 1.0564
- Overround: 1.0564 − 1 = 5.6%
- Share of total stakes: 0.0564 ÷ 1.0564 = 5.3%
Both measures describe the same market. When someone quotes a margin, check which of the two they mean. Try the odds of a market in the margin calculator.
Why there are two measures
Imagine you split €105.64 across the three outcomes so that you always receive the same amount: €54.05 at 1.85, €27.78 at 3.60 and €23.81 at 4.20. Whatever the result, you receive €100.
- The operator keeps €5.64. Compared with the €100 paid out, that is 5.6%: the overround.
- Compared with the €105.64 staked, it is 5.3%: the share of total stakes.
The theoretical return is 1 ÷ S = 94.7% of the total staked.
The margin is spread across every outcome in the market, so you pay it whatever you choose.
Odds without the margin
To see a market’s odds without the margin, multiply each price by S. In the example: 1.85 × 1.0564 = 1.95; 3.60 × 1.0564 = 3.80; 4.20 × 1.0564 = 4.44. This is the proportional method, the simplest one; there are others.
Two markets, two margins
| Market (example) | Odds | S | Overround | Share of total stakes |
|---|---|---|---|---|
| Two outcomes | 1.90 / 1.90 | 1.0526 | 5.3% | 5.0% |
| Three outcomes | 1.85 / 3.60 / 4.20 | 1.0564 | 5.6% | 5.3% |
The numbers are examples for the calculation, not any operator’s prices.
What it means in practice
If you stake €100 in total on markets with a 5% share-of-stakes margin, the expected cost is about €5, whatever you choose. On a single match the result may be different, up or down. The more you bet, the more your overall result tends towards the cost of the margin. In multiple bets the margin compounds: see the guide Bet types.
A smaller margin lowers the cost; it does not create a profit. SRIJ recommends that advertising should not create the illusion of winning large sums or present gambling as free of financial risk (good-practice manual, §5).
Official sources
- RJO (Annex I to Decree-Law 66/2015), consolidated text published by SRIJ: Art. 4(a) (Portuguese)Checked 15/10/2026
- SRIJ · Publicidade de Jogos e Apostas: Manual de Boas Práticas (advertising good-practice manual), §5 (Portuguese)Checked 13/10/2026
Frequently asked questions
Which of the two measures is “the” margin?
Both are used. The overround (S − 1) measures the excess above 100%; the share of total stakes ((S − 1) ÷ S) measures the part of every euro staked that the operator keeps. In the 1.85 / 3.60 / 4.20 example they are 5.6% and 5.3%. When you compare markets, always use the same measure.
Is the margin the same in every market?
No. Each market has its own, even within the same match. Work it out market by market.
If I always choose the shortest odds, do I avoid the margin?
No. The margin is spread across every outcome in the market, so you pay it whatever you choose.