Rough estimate of vigorish/juice?

I found this nice handy tool wizardofodds.c0m/games/sports-betting/straight-bet-calculator/

But I'm wondering is there a way to quickly guess in your head what the house edge is?

For example, estimating 1.68/2.33 in your head

Or if you prefer American format, something like estimating -162/+128

Yes. The fair odds are the ratio of the implied probabilities. For example, for -162/+128 the fair price is 162/262 * 228 = 140.98 or -141/+141. The juice is 1 - 228 /241 = 5.4%

The method I use is to work out how much you would have to bet to get back $100 regardless of which horse/event wins.

So in this example you would need to place $61.83... (at -162 i.e. 162/262) and $43.86... (at +128 i.e.100/228) for a total of $105.6917.

Others may, quite reasonably, prefer to see what they would expect to win for ever y $100 wagered, so this is $94.6148.

Looking at 1.68 and 2.33 (such as found on betfair) is slightly easier as the calcualtions are 100/168 and 100/233 to give $102.4423.

At the racetrack one gets to know the percentages, so a four horse race with typical odds, 6/4=.40 5/2=.286 3/1=.25 7/1=.125 so that would be about 106.1% book.

How I do it:

When no-vig line is around +100:
-20-cent line (ie -110 / -110) house edge is 4.5%
-10-cent line is half that, or 2.3%
-five-cent line is half that again, or 1.2%

When no-vig line is around +200
-40-cent line (ie -220 / +180) is 4.5%
-20-cent line is 2.3%
-10-cent line is 1.2%
-five-cent line is 0.6%

When no-vig line is around +300
-80-cent line (ie -350 / +270) is 4.5%
-40-cent line is 2.3%
-20-cent line is 1.2%
-10-cent line is 0.6%
-five-cent line is 0.3%

For -162 / +128 I would call that a 40-cent line and in between +100 and +200, or in between 4.5% and I guess 9%. Or 6.75%. But I would know that is high because it's really a 35-cent line, the no-vig price is closer to +100 and a 40-cent line at +100 is actually 8%, not 9%. I could say with 100% certainty the house edge is between 4.54% and 6.75% and 90% certainty that it is between 5% and 6%.

Can only do this because I have much more experience with American odds. If it was decimal odds, most viable option would be to ask my calculator.

If fair odds are +200/-200, 4.5% vig will give +187/-231 (rounded)

If fair odds are +300/-300 4.5% vig will give +282/-366 rounded)

(Edit: just realized I misread the question. Below isn’t really on point to question of how to do it in your head).


I just use an online calculator. I don’t want to advertise a non-Mike site so I won’t name one but they’re available and free. Of course you may be looking for a rough rule of thumb when you need an answer quick and can’t plug numbers into a form. Others are better at that math than I am.

Quote: TomG

How I do it:

When no-vig line is around +100:
-20-cent line (ie -110 / -110) house edge is 4.5%
-10-cent line is half that, or 2.3%
-five-cent line is half that again, or 1.2%

When no-vig line is around +200
-40-cent line (ie -220 / +180) is 4.5%
-20-cent line is 2.3%
-10-cent line is 1.2%
-five-cent line is 0.6%

When no-vig line is around +300
-80-cent line (ie -350 / +270) is 4.5%
-40-cent line is 2.3%
-20-cent line is 1.2%
-10-cent line is 0.6%
-five-cent line is 0.3%

For -162 / +128 I would call that a 40-cent line and in between +100 and +200, or in between 4.5% and I guess 9%. Or 6.75%. But I would know that is high because it's really a 35-cent line, the no-vig price is closer to +100 and a 40-cent line at +100 is actually 8%, not 9%. I could say with 100% certainty the house edge is between 4.54% and 6.75% and 90% certainty that it is between 5% and 6%.

Can only do this because I have much more experience with American odds. If it was decimal odds, most viable option would be to ask my calculator.
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This is nice! thanks