What Is Bookmaker Margin?
Bookmaker margin is the edge built into the odds so the bookmaker profits over time. Add up the implied probabilities of every outcome in a market. The amount above 100 percent is the margin, also called the overround.
Bookmaker margin example: Gor Mahia vs AFC Leopards
Here is a 1X2 market. "1X2" means home win (1), draw (X) or away win (2).
| Outcome | Odds (example odds) | 1 ÷ odds × 100 |
|---|---|---|
| Gor Mahia win (1) | 2.40 | 41.67% |
| Draw (X) | 3.10 | 32.26% |
| AFC Leopards win (2) | 3.00 | 33.33% |
| Total | 107.26% |
Only one result can happen, so a fair market would total 100 percent. This one totals 107.26%. The margin is 7.26%.
Say you stake (the money you bet) KSh 100 on Gor Mahia. If the match ends 2–1 to Gor Mahia, you get KSh 100 × 2.40 = KSh 240. The margin means that price is a little lower than fair.
What is the margin formula?
The margin formula is: add 1 ÷ odds for every outcome, multiply by 100, then subtract 100.
- Overround = (1 ÷ odds A + 1 ÷ odds B + 1 ÷ odds C) × 100
- Margin = overround − 100
You can also find the payout percentage. That is the share of stakes the odds return on average.
- Payout percentage = 100 ÷ overround × 100
For the Gor Mahia market: 100 ÷ 107.26 × 100 = 93.23%. On average, these odds pay back about KSh 93.23 for every KSh 100 staked. The rest, about 6.77%, is what the bookmaker keeps.
Our implied probability guide explains the 1 ÷ odds step in more detail.
Two-way market example
A two-way market has only two outcomes, such as over or under 2.5 goals. The same formula works with two prices.
Say over 2.5 goals and under 2.5 goals are both 1.90 (example odds).
- 1 ÷ 1.90 × 100 = 52.63% for each side
- Overround = 52.63% + 52.63% = 105.26%
- Margin = 5.26%
The fair price for a 50/50 outcome would be 2.00. The bookmaker offers 1.90 on both sides instead.
How to compare margins between markets
To compare margins, work out the overround for each market and pick the lower number. A lower margin means odds closer to fair.
| Market | Odds (example odds) | Overround | Payout percentage |
|---|---|---|---|
| 1X2, Gor Mahia vs AFC Leopards | 2.40 / 3.10 / 3.00 | 107.26% | 93.23% |
| Over/under 2.5 goals | 1.90 / 1.90 | 105.26% | 95.00% |
| Over/under 2.5 goals | 1.80 / 2.00 | 105.56% | 94.74% |
Margins are often higher on smaller leagues and unusual markets. Big matches and main markets often have lower margins. Check the prices yourself rather than assume.
A lower margin does not make a pick more likely to win. It only means you pay a smaller price for the bet.
Why accumulators multiply the margin
Accumulators multiply the margin because each pick carries its own margin. When you multiply the odds, you also multiply the bookmaker's edge.
Take three picks, each a fair 50/50 chance. Each is priced at 1.90 instead of a fair 2.00 (example odds).
| Bookmaker odds | Fair odds | Share paid back on average | |
|---|---|---|---|
| 1 pick | 1.90 | 2.00 | 95.00% |
| 2 picks | 3.61 | 4.00 | 90.25% |
| 3 picks | 6.86 | 8.00 | 85.74% |
The working for 3 picks:
- Bookmaker odds: 1.90 × 1.90 × 1.90 = 6.859, shown as 6.86
- Fair odds: 2.00 × 2.00 × 2.00 = 8.00
- Share paid back: 6.859 ÷ 8.00 = 85.74%
So a single keeps about 5% for the bookmaker. A 3-pick accumulator keeps about 14.26%. More picks means a bigger cut. See our accumulator bet guide.
What does margin mean for your long-run results?
Over many bets, the margin pulls your results below zero unless you find better prices than the bookmaker. It is the main reason most bettors lose money over time.
Say you place 100 singles of KSh 100 each, all on markets paying back 95%.
- Total staked = 100 × KSh 100 = KSh 10,000
- Expected return = KSh 10,000 × 95% = KSh 9,500
- Expected loss = KSh 500
Your real result will be higher or lower, because luck matters. But the average points down. To track your own results, read ROI and yield. To learn when a price may beat the margin, see value bet.
Common mistakes
- Ignoring the margin. Every market has one, even if you cannot see it.
- Thinking big odds hide no margin. Long accumulators carry the largest total margin.
- Assuming all markets are equal. Margins vary by league and market type.
- Confusing low margin with a likely win. A low margin only means a fairer price.
FAQ
Is bookmaker margin the same as overround?
They are closely linked. The overround is how far the implied probabilities go above 100 percent. People often call that number the margin.
Can I avoid the bookmaker margin?
No. Every price a bookmaker offers includes a margin. You can only choose markets where it is smaller.
Is a lower margin a sign of a better bet?
It means the odds are a little closer to fair. It does not make your pick more likely to win.