How to use the margin calculator
- Pick one market at one bookmaker: a match result, a tennis match winner, a basketball moneyline.
- Enter the decimal odds of every outcome. Two for a market without a draw, three for a football 1X2. Odds in another format? Convert them first with the odds converter.
- Read the totals: the sum of the implied probabilities, the margin (or overround) and the payout rate. For each outcome, you also get its implied probability, its probability without the margin and the fair odds that go with it.
Say a basketball moneyline is priced 1.87 and 1.95. The implied probabilities are 53.5% and 51.3%, for a total of 104.8%. The margin is 4.8% and the payout rate 95.5%. Without the margin, the two sides stand at 51.0% and 49.0%, which means fair odds of 1.96 and 2.04.
The formulas behind it
Total = 1 ÷ odds 1 + 1 ÷ odds 2 (+ 1 ÷ odds 3)
Margin (overround) = total − 100%
Payout rate = 100% ÷ total
Fair probability = (1 ÷ odds) ÷ total, and fair odds = 1 ÷ fair probability
Spreading the margin in proportion to each implied probability, as above, is the simplest method and the one the calculator uses. Other methods load more of the margin onto long shots; our guide to implied probability explains why the choice matters little on most markets.
What a given margin means
The margin and the payout rate are two views of the same thing. The table shows what common margins leave to bettors as a group, on average.
| Margin (overround) | Total | Payout rate | Kept per $100 staked |
|---|---|---|---|
| 3% | 103% | 97.1% | $2.91 |
| 5% | 105% | 95.2% | $4.76 |
| 8% | 108% | 92.6% | $7.41 |
| 12% | 112% | 89.3% | $10.71 |
Margins tend to be lowest on the main markets of big events and higher on minor leagues, player markets and in-play betting. Try a lesser-known market: 1.80, 3.30 and 4.00 add up to 110.9%, a margin of almost 11%. And because a parlay multiplies the odds of its legs, it multiplies their margins too: the bet calculator and our article on parlays and singles show what that does to the return.
Overround, vig and juice
In the United States, the margin is called the vig or the juice. A market at −110 on both sides is the classic case: −110 is 1.91 in decimal, so the total is 104.8% and the overround 4.8%.
Some sites quote a slightly smaller figure for the same market, 4.5%. They measure the share of all stakes the bookmaker keeps: if one bettor stakes $110 on each side, $220 goes in, $210 comes back to whoever wins, and $10 stays with the bookmaker. Both figures describe the same prices; this calculator shows the overround and the payout rate.
Mistakes that give a wrong margin
- Mixing bookmakers. Taking the best price for each outcome from different bookmakers can bring the total close to or under 100%. That says nothing about any one bookmaker’s margin.
- Mixing markets. “Home win” from the 1X2 market and “away” from a draw-no-bet market do not belong together.
- Leaving out an outcome. Forget the draw in football and the total falls well under 100%; the calculator warns you when that happens.
- Using prices from different moments. Odds move. Enter them all at the same time.
- Entering a boosted price. A boost changes one outcome only, so the result no longer describes the market as the bookmaker normally prices it.
Frequently asked questions
What is a bookmaker margin?
It is the amount by which the implied probabilities of all the outcomes of a market exceed 100%. The bookmaker builds it into every price, so bettors as a group get back less than they stake.
What does a payout rate of 95% mean?
On average, $95 of every $100 staked on that market goes back to bettors, and $5 stays with the bookmaker. It describes the market as a whole, not what any one bettor will get back.
How do I calculate fair odds?
Add up the implied probabilities of every outcome, divide each one by that total to get its fair probability, then take 1 ÷ fair probability. The calculator does all three steps.
Why does the calculator say the total is under 100%?
The odds do not come from one complete market at one bookmaker: an outcome is missing, or the prices come from different bookmakers or markets.
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