Synthetic Line Shopping: Comparing Apples to Oranges
This is the part many bettors skip, and it's hugely important: the market often gives you multiple ways to express the same opinion, but not at the same number.
You're not just shopping books. You're shopping expressions of the bet.
The Challenge of Different Lines
You might be choosing between:
- Lawrence Over 1.5 pass TDs at -190
- Lawrence Over 2.5 pass TDs at +135
You can't compare those by vibes. You compare them by EV.
To do that, you need two things:
- The price (odds)
- Your estimate of the probability of each event
Key Insight
The question isn't "which one hits more?" The question is "which one pays me more relative to how often it hits?"
Worked Example: QB Passing Touchdowns
Let's say your model implies:
- P(Lawrence throws 2+) = 62%
- P(Lawrence throws 3+) = 44%
Now compute EV for each, risking $100 per bet.
Step 1: Calculate Profit if Win
Profit if Win (Negative Odds)
Profit = Stake × (100 / |Odds|)=A1*(100/ABS(B1))Profit if Win (Positive Odds)
Profit = Stake × (Odds / 100)=A1*(B1/100)| Bet | Odds | Profit if Win |
|---|---|---|
| Over 1.5 TDs | -190 | $100 × 100/190 = $52.63 |
| Over 2.5 TDs | +135 | $100 × 135/100 = $135.00 |
Step 2: Calculate Expected Value
Expected Value
EV = (Win Probability × Profit) - (Loss Probability × Stake)=(A1*B1)-((1-A1)*C1)Over 1.5 at -190:
EV = 0.62 × $52.63 - 0.38 × $100
EV = $32.63 - $38.00
EV = -$5.37 ❌
Over 2.5 at +135:
EV = 0.44 × $135 - 0.56 × $100
EV = $59.40 - $56.00
EV = +$3.40 ✅
Warning
Even though the "safer" play (Over 1.5) wins more often, the price makes it worse. The higher-variance Over 2.5 is actually the +EV bet in this scenario.
Where Synthetic Line Shopping Shows Up
This comparison happens across every sport:
| Sport | Example Comparisons |
|---|---|
| NBA | Over 6.5 assists -150 vs Over 7.5 assists +110 |
| NFL | Over 59.5 rushing yards -130 vs Over 69.5 yards +110 |
| MLB | Over 1.5 total bases -120 vs 2+ hits +150 vs HR +200 |
| NHL | Anytime goal +180 vs 2+ points +300 |
Each of these requires you to:
- Estimate the probability of each outcome
- Calculate the EV at the given price
- Choose the option with the highest EV (or pass if both are negative)
The Decision Framework
┌─────────────────────────────────────┐
│ SYNTHETIC LINE SHOPPING FLOW │
├─────────────────────────────────────┤
│ 1. Identify all available lines │
│ for the same player/prop type │
│ │
│ 2. Estimate probability for each │
│ threshold using your model │
│ │
│ 3. Calculate EV for each option │
│ │
│ 4. Compare EVs: │
│ • If one is positive → bet it │
│ • If multiple positive → bet │
│ the highest EV │
│ • If all negative → pass │
└─────────────────────────────────────┘
Tip
This is where tools become a real edge. Doing these calculations manually across many books and alt lines is slow—and slow is expensive when lines move.
Common Mistakes in Synthetic Comparison
Mistake 1: Always Picking the "Safer" Bet
Higher-probability bets feel safer, but they're often priced accordingly. The -190 on Over 1.5 TDs looks "safe," but the price already reflects that safety.
Mistake 2: Ignoring Lower Lines
Many bettors only look at the main number. If the standard line is 24.5, they don't consider Over 22.5 or Over 26.5 as alternatives.
Mistake 3: Comparing by Odds Instead of EV
"+135 is better than -190" is only true if the probabilities support it. Always calculate the actual EV.
Expected Value Calculator
Try the interactive calculator for this concept
📝 Exercise
Instructions
Practice comparing alt lines using EV calculations.
Exercise 13.2: Synthetic Line Comparison
Scenario: You're analyzing Saquon Barkley rushing props. Your model gives these probabilities:
| Threshold | Your Probability |
|---|---|
| Over 74.5 yards | 58% |
| Over 84.5 yards | 45% |
| Over 94.5 yards | 32% |
Available odds:
| Line | Odds |
|---|---|
| Over 74.5 yards | -145 |
| Over 84.5 yards | -105 |
| Over 94.5 yards | +130 |
Your task: Calculate the EV for each line and determine which (if any) you should bet.
Key Takeaway
Key Insight
Synthetic line shopping expands your opportunity set dramatically. You're not limited to the standard line—you can find +EV on alt lines that the market has mispriced relative to the main number. Always compare EV, not just odds or hit rates.