New Traders Get $10 on Kalshi
CODE: LINESTARTrade event contracts on sports, economics & more. Sign up with promo code LINESTAR.
MLB Synthetic Run Line Calculator
Build a synthetic -1 (favorite) or +1 (underdog) run line by splitting a moneyline and a 1.5 run line bet. See the exact stake split, the effective price, and whether the play actually beats a straight moneyline or run line.
Stake Allocation
Moneyline Stake
$60.00
@ -150
-1.5 Run Line Stake
$40.00
@ +130
Outcome Scenarios
Effective Synthetic -1 Price
-109
Decimal 1.920
Break-Even Rate
52.1%
How often the 2+ run win must hit (1-run = push) to profit.
When to Use a Synthetic Run Line
A synthetic run line splits one stake across a moneyline bet and a 1.5 run line bet so that a one-run game becomes a push instead of a loss. Around 28-30% of MLB games are decided by a single run, so converting that result from a loss to a refund is valuable — but only when the price is right.
Lean Synthetic -1 (favorite) when…
- You like a favorite but don't trust a full -1.5 cover.
- The matchup projects close (strong bullpens, low total).
- The -1.5 price is juicy (+120 or better) relative to the moneyline.
Lean Synthetic +1 (underdog) when…
- You back a live dog you think keeps it close.
- You want outright-win upside plus 1-run-loss insurance.
- The +1.5 is heavily juiced and the moneyline pays well.
Use the Is It Worth It? tab before betting. If a straight moneyline or straight 1.5 run line shows higher expected value for your margin estimates, take the simpler bet — the synthetic only wins when the 1-run push is worth more than its cost.
Keep Sharpening Your Edge
This calculator is for informational and educational purposes only. Results should be verified with your sportsbook before placing any wagers. All betting carries risk. Full Disclaimer
How to Use This Calculator
- 1Pick Favorite or Underdog: Choose whether you're building a synthetic -1 (favorite) or +1 (underdog) run line.
- 2Enter Moneyline Odds: Input the current moneyline odds for your team (e.g., -150 or +130).
- 3Enter the 1.5 Run Line Odds: Input the -1.5 (favorite) or +1.5 (underdog) run line odds.
- 4Set Total Stake: Enter the total amount you want to risk across both legs.
- 5Review the Split & Outcomes: See exactly how much to bet on each leg and the payout for every margin.
- 6Check the EV Analyzer: Estimate margin probabilities to see if the synthetic beats a straight bet.
Frequently Asked Questions
What is a synthetic -1 run line?
A synthetic -1 run line combines a moneyline bet on a favorite with a -1.5 run line bet in specific proportions. A 1-run win becomes a push (money back), a 2+ run win profits, and a loss costs your full stake — effectively a -1 line that books rarely offer directly.
What is a synthetic +1 run line?
The underdog mirror image. You split your stake between the underdog moneyline and the +1.5 run line so that an outright win profits, a 1-run loss becomes a push, and a 2+ run loss costs your stake. It's a synthetic +1 for dogs.
Why would I want a synthetic run line?
Roughly 28-30% of MLB games are decided by exactly one run. A synthetic line converts that high-frequency 1-run result from a loss into a push, lowering variance while keeping upside on multi-run margins.
Is the synthetic always better than a straight bet?
No. You pay for the push protection through a worse effective price. Use the 'Is It Worth It?' tab to compare expected value against a straight moneyline and a straight 1.5 run line based on your own margin estimates.
Is this legal?
Yes. You are placing two separate, ordinary bets that combine into a different risk profile. It is a common, legitimate strategy among sharp bettors.
Props Optimizer
Take your sports betting analysis to the next level with Props Optimizer - tools and data to help you make more informed decisions.
Try Props Optimizer Free$ Partner Bonuses
Responsible Gambling
Gambling should be entertaining, not a way to make money. Only bet what you can afford to lose, and never chase your losses.
- Betting more than you can afford to lose
- Chasing losses with bigger bets
- Lying to others about gambling habits