In conclusion to the preceding tip on value betting, the following instructions are for determining just how much money you should bet on a value bet.  Depending on the assigned odds of the bet and the subjective probability of winning (which you assign to the bet), the amount of your stake can range considerably.  The formula used for calculating the percentage of one's bankroll to place on a value bet was created by the well-known professional gambler, John Kelly.

The formula must have the following variables in order to work:  Probability of bet winning, which should be expressed in decimals.  For instance, if you believe the probability of you bet winning to be 57%, the decimal expression of this is .57.  The other variable you will need to plug into the formula are the odds dictated by the sportsbook.

Kelly's formula looks like this:   Advantage = Probability - [(1 - Probability) ÷ (odds - 1)].  The calculated value of Advantage should then be converted into a percentage by multiplying it by 100.  This then, is the percentage of one's bankroll that should be staked on the odds.

For a bet with odds of 2, and probability of .6 (60%), the calculation would look like this:
A = .6 - [(1 - .6) ÷ (2 - 1)] = .6 - [.4 ÷ 1] = .6 - .4 = .2 = 20%

For this particular bet, one should bet no more or less than 20% of their bankroll.  Just keep in mind that the determination of the probability of winning is a vital step.  If you overestimate this value, you will likely lose money.  If you underestimate the probability, you will not lose money, but you will not win as much. Obviously, the safer route is to underestimate the probability when in doubt.  Be sure to do all of your research ahead of time, giving yourself the proper knowledge to make an accurate assessment of the probability.