Percentage needed to break even with a dime spread

BigGamesOnly · Jul 26, 2003

When asked what percentage of games you would need to win in order to break even in a 100/110 spread, quite a few people would say 55% since 55% is half of 110%. That number is not correct.

I have been doing some calculating to find out what percentage of bets you would need to win if you were betting a 100/110 spread. As you can see my calculations are pretty much common algebra. Please feel free to point out any mistakes/discrepancies as you see fit.

Keep in mind these calculations are valid only if you are using the same amount on each bet. Most individual bets aren't +100/-110 but if you are getting a dime spread they eventually even out to 100/110 in the long run.

Here is an explanation of variables-

X = number of games won
Y = number of games lost
N = total number of games played
T = number of ties
(For our purposes, T = 0 since ties are a no bet and will not be included in these calculations.)

We are looking for the value of X divided by the value of N to get the percentage of wins. That would be notated as:

X/N

The equation to use to calculate the break-even point is:

X times 100 = Y times 110
(you put up 110 to win 100)

or

100X = 110Y

Also:

X + Y = N
(the number of times you win plus the number of times you lose equals the total number of games you play.

This leads to:

Y = N - X

If you substitute N - X for Y in the previous equation you get:

100X = (N - X)*110

100X = 110N - 110X

210X = 110N

210X/N = 110

X/N = 110/210

X/N = 52.38%

You would need to win 52.38% of the time to break even.

Guest · Jul 26, 2003

Sorry, but your calculation method is wrong. You aren't solving break even price for DIME-line. You calculated break even price for -110.

I made EXCEL helper couple days ago to solve break even price and for odds converting:

http://therxforum.com/6/ubb.x?a=tpc&s=100090022&f=8183022525&m=92110472

10 cent line(-105/-105), break even % 51.23
20 cent line(-110/-110), break even % 52.38
30 cent line(-115/-115), break even % 53.48

And break even % for different odds:

-120=54.56
-125=55.56
-130=56.53
-135=57.44
-140=58.34
-145=59.17
-150=59.99
-155=60.79
-160=61.54
-165=62.27
-170=62.97
-175=63.65
-180=64.27
-185=64.89
-190=65.53
-195=66.09
-200=66.67

Ans so on.......

BigGamesOnly · Jul 26, 2003

Pardon my ignorance but when I made mention of wagering 110 to win 100 I thought that was called a "dime line".

Wouldn't that be the same thing as -105/-105? Yet our percentages are different.

Thanks for the help.

Guest · Jul 27, 2003

I made a mistake with telling this:

10 cent line(-105/-105), break even % 51.23.
20 cent line(-110/-110), break even % 52.38
30 cent line(-115/-115), break even % 53.48

That was incorrect. Those are just break even prices for different odds.

-105=51.23
-110=52.38
-115=53.48

*************************

Well, actually you were right. You talked about "dime spread" and break even % is 52.23 in this case (-110), that's right, but thats not a dime line. It's only break even price for -110. A dime line is when spread is 10 cents and bookmakers vig about 2.4%, if teams are equal. 20 cent line means 20 cent spread and the vig is about 4.5%, if teams are equal.
You have to calculate break even prices for both odds to solve dime line vig.

Lets see:

A line is -110/+100 With a -110 break evevn is 52.38 and with +100 it is 50. Then calculate 52.38+50=102.38. Now we have to solve bookmakers vig when odds are -110/+110:

100/102.38=97.68 and 100-97.68=2.32%

The vig isn't always the same.

-105/-105=2.40%
-110/+100=2.32%
-115/+105=2.21%
-120/+110=2.13%
-125/+115=2.03%
-130/+120=1.95%
-135/+125=1.85%
-140/+130=1.79%
-145/+135=1.70%
-150/+140=1.63%
-155/+145=1.58%
-160/+150=1.51%
-165/+155=1.46%
-170/+160=1.41%
-175/+165=1.37%
-180/+170=1.29%
-185/+175=1.24%
-190/+180=1.23%
-195/+185=1.17%
-200/+190=1.14%

Beacuse vig gets lower, bookmakers usually start to use 20-cent line, when line reach -155 or something like that.