A lesson in converting odds to percentages

Hey

In the Sports section, I want to encourage more people to base their initial starting percentages for sporting events on the odds offered by online gambling sites/oddsmakers. One of the best sites for this is oddschecker.com which aggregates odds from a range of sources.

So heres how to convert the fractional odds quoted into approximate outcome percentages for Hubdub:

- Odds will typically be quoted in a fractional or over/under format.
For example NBA: Cleveland @ Boston on Feb 28th: Oddschecker quotes Cleveland at 45/17 and Boston at 1/4

- To calculate the percentages for an outcome: divide the under number (denominator) by the sum of the over (numerator) and under (denominator) numbers. Heres the formula: (under/(over + under)) * 100 = outcome percentage

In the example above:

Cleveland - (17 / (45 + 17)) * 100 = 27 (27%)

Boston - (4 / (1 + 4)) * 100 = 80 (80%)

But 27% + 80% is 107%? - The sum of the calculated percentages will always be over 100%. The additional percentage over 100% (7% in the example) is what the gambling site make their revenue from.

To comply with the Hubdub rule that outcomes must add up to 100%, just take a few percentage points off each percentage so that the percentages add up to 100% and the ratio of the percentages with respect to each other remains similar. In the example above setting Cleveland to 25% and Boston to 75% would be acceptable.

Hope this helps and encourages more of you to set more accurate starting percentages.

Regards

Donal
(Hubdub Sports Editor)