The True Odds calc can be used to work out what a bookmakers odds for a market would be if their margin was removed. In other words, it shows what the bookie really thinks the odds should be.

This calc is particularly useful when we want to know the probability of an outcome but Betfair doesn’t have a market for it. It can also be used when Betfair does have a market but liquidity is poor.

The true odds can be used when calculating expected value, or just to get an idea of how big a margin the bookie is applying.

Using the Calc

This is a very easy calculator to use. If we want to work out the true odds of a market we just enter the bookie odds for each of the selections. Here is what it would look like for an NRL game between Penrith and Canberra:

Our True Odds Calculator uses four different methods so that you can see the range of possibilities:

Equal Margin (EM), Margin Proportional to Odds (MPTO), Odds Ratio (OR) & Logarithmic (LOG) Methods.

For an explanation of each method, see this article.

Adding Rows

If you are looking at a market with more than two potential outcomes you can add more rows by pressing the “Add Outcome” button. You can add as many rows as you need.

Video Explainer