What this page sets up
The calculator opens on the vig tab with a three-way soccer market: home +140, draw +240, away +185. Enter the odds for every outcome of one market, from one book, and add or remove outcomes as needed: two for a spread, total or tennis match, three for a soccer 1X2 market, more for a race or a futures market. The result shows the book’s margin and a table of each outcome’s implied chance, fair chance and fair odds.
Using fair odds
Fair odds are the best estimate of the true chances that the book’s own prices give you. Compare them with a price at another book: if another book offers longer odds than the fair price on the same outcome, that bet has positive expected value by this estimate. Sharp books with low margins give the most reliable fair odds.
What counts as a low margin
The table under this text lists common two-way lines with their margin. A market at −105 on both sides takes about 2.4%; the standard −110 takes 4.55%, and lopsided lines often take more. Three-way and futures markets usually carry larger margins because there are more outcomes to price: the three prices this page opens with add up to 106.17%, a margin of 5.81%.
Margin and fair odds on common two-way lines
| Line | Book total | Margin (vig) | Fair odds | Fair chance |
|---|---|---|---|---|
| −105 / −105 | 102.44% | 2.38% | +100 / +100 | 50% / 50% |
| −110 / −110 | 104.76% | 4.55% | +100 / +100 | 50% / 50% |
| −115 / −105 | 104.71% | 4.5% | −104.43 / +104.43 | 51.1% / 48.9% |
| −120 / +100 | 104.55% | 4.35% | −109.09 / +109.09 | 52.2% / 47.8% |
| −130 / +110 | 104.14% | 3.98% | −118.7 / +118.7 | 54.3% / 45.7% |
| −150 / +130 | 103.48% | 3.36% | −138 / +138 | 58% / 42% |
| −200 / +170 | 103.7% | 3.57% | −180 / +180 | 64.3% / 35.7% |
| −300 / +240 | 104.41% | 4.23% | −255 / +255 | 71.8% / 28.2% |
Maths only, not betting advice. If gambling stops being fun, free confidential help is listed on the odds calculator page.