In about five minutes this page gives you a dollar stake for any alternate run line, from -3.5 on a favorite to +2.5 on an underdog. Know one thing first: the further the line moves from 1.5, the smaller the stake, however good the price looks. Betting for Baseball puts roughly 28% of MLB games at a one-run margin and about 18% at exactly two. A favorite laying -2.5 has to get past both of those groups before it pays you.

What you need

  • Your current bankroll

    The figure in your accounts today, not the one you started the season with.

  • A unit percentage between 1 and 3%

    MLBBeatBets calls 1.5 to 2% the sweet spot for most bettors.

  • The alternate price at two or more books

    BettingUSA's advice is to shop alternates specifically, because they draw less attention than the standard line.

  • Somewhere to log the bet and its closing price

Six steps from bankroll to ticket

1. Turn your unit into dollars. Multiply your current bankroll by your unit percentage. "A unit is a percentage, not a fixed dollar," as OddsShopper puts it, so the result moves when the bankroll does. You should end up with a single dollar figure. The bet sizing calculator will do the arithmetic for you.

2. Put the line in a bucket. The buckets are standard (-1.5 or +1.5), one step out (-2.5), or wider (-3.5 and beyond). Choose the bucket before you look at the payout. The payout is the bait, and it is also why the odds jump so sharply.

3. Apply the bucket's multiplier. Betting for Baseball's framework is a full unit on standard lines, a half unit on -2.5, and a quarter unit on anything wider. The exception is an underdog at +2.5, which can take up to a full unit because it hits much more often, even though the heavy juice cuts what each win pays. Read "up to" as a ceiling. MLB Betting Systems says +2.5 usually costs -300 or worse and is "rarely justified." I'd pass on most of them and give a full unit only to the few you have priced yourself.

4. Check the stake against your cap. MLBBeatBets says professionals cap any single bet at 3%, even when they size with fractional Kelly. OddsShopper's absolute ceiling is about 5%. With these multipliers an alternate should sit well below either figure. If it gets close, your unit is too big.

5. Count tonight's -2.5 tickets. Keep it to one. Several -2.5 bets on one slate are all wagers on the same unlikely outcome, a multi-run win. Betting for Baseball warns that stacking them "multiplies your risk in a way that a single -2.5 position does not." You should have one wide favorite on the night, or none.

6. Log it. Record the line, the price and the stake, and add the closing price later. After a month the log shows whether your -2.5 bets are beating their breakeven or only feeling as if they do.

A $2,000 bankroll at a 2% unit

This is a hypothetical night. The -2.5 is priced at +180, which sits inside the +150 to +220 range MLB Betting Systems gives for that line.

Unit (2% of $2,000)$40
Standard -1.5, full unit$40
-2.5 at +180, half unit$20 to win $36
-3.5, quarter unit$10
+2.5 underdog, ceiling$40

The wide favorite now risks a quarter of what the standard line does, so a cold run costs you dollars you can replace instead of weeks of recovery.

When the sizing feels wrong

Probably not. Betting for Baseball describes exactly that run, six straight -2.5 losses, and notes it is ordinary for a bettor hitting about 40%. OddsShopper adds that even a 55% bettor should expect losing streaks of six to eight. Leave the multiplier where it is. If you are tempted to raise it, read what to do mid-slump first.

This is the strongest case for sizing up. Doc's Sports points out that a +260 line breaks even at a 28% win rate, compared with 38% at +160. That is correct, and it describes the long run. It doesn't change how the losses cluster along the way. A lower breakeven tells you whether a bet is worth making. The size of the stake is what determines whether you survive the losing stretches.

Kelly is only as accurate as your win-probability estimate, and estimating a two-run margin is hard. OddsShopper notes that "almost no one uses full Kelly," and that when the true edge shrinks slightly, even the half-Kelly stake falls sharply. Use whichever is smaller, Kelly or the multiplier.

Done, and then

You now have a fixed stake for every alternate number on the board and a cap that stops a big payout from tempting you into a bigger bet. The next job is applying that unit across the full game card, where moneylines and totals compete with run lines for the same bankroll.

How does this unit fit across moneylines, run lines and totals?

The pillar guide covers all three MLB bet types and shows how one bankroll handles them together.

Read the MLB strategy guide