Overround calculator
Add up the chances a bookmaker's prices imply, see the margin built into the market, and each outcome's price with that margin taken out.
Try it
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Free to use. It works in your browser, and nothing you type leaves it.
How it works
Each price implies a chance: 100 divided by the decimal odds. Over a complete market, with one price for every outcome, those chances add up to more than 100%. The excess is the overround, the margin built into the prices. Taken out in proportion, it leaves each outcome a chance and a price with no margin in them.
Worked through
A three-way market priced at 6/5, 12/5 and 9/4.
| Price | Implied | No margin | Price, no margin |
|---|---|---|---|
| 6/5 | 45.45% | 43.03% | 2.32 |
| 12/5 | 29.41% | 27.84% | 3.59 |
| 9/4 | 30.77% | 29.13% | 3.43 |
| It shows | Value |
|---|---|
| Book | 105.64% |
| Overround | 5.64% |
The three implied chances add up to 105.64%. Taking the margin out in proportion lengthens every price a little.
Questions
Why do the implied chances add up to more than 100%?
Because the prices carry the bookmaker's margin. Prices with no margin would add up to exactly 100%, and the amount over that is the overround.
Can I compare bookmakers with it?
Yes. Enter one bookmaker's prices for every outcome of a market, then another's for the same market. The lower book percentage carries the smaller margin.
How is the margin taken out?
In proportion. Each outcome's implied chance is divided by the book percentage, so every outcome gives up the same share. Other methods put more of the margin on the longer prices, so their figures differ a little.
Free to embed
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For the prices themselves, see the Raw odds feed.
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