Sports Prop Bet Calculator: Beyond the Final Score

Prop bets focus on specific events within a game—player stats, in-game occurrences, or alternative outcomes. Our calculator shows implied probability for any prop, helping identify value when your projections differ from the market.

What Are Prop Bets?

Proposition bets (props) are wagers on specific outcomes other than the final score. Player props bet on individual performance (rushing yards, points scored). Game props bet on specific events (first team to score, total turnovers). Same-game parlays combine multiple props.

Quick Answer: Props bet on specific outcomes: Player over/under stats, game events, alternative lines. Implied probability calculation same as any bet. Convert odds to probability, compare to your estimate. Value exists when your probability > implied probability. Props often have higher juice (vig) than main lines—factor this into decisions.

How to Use Our Calculator

Use the Prop Bet Calculator →

Enter prop odds to see implied probability and potential value.

Step-by-Step Instructions

1. Enter Prop Odds: American or decimal

2. View Implied Probability: What odds suggest

3. Input Your Estimate: What you think

4. Calculate Edge: Your advantage

5. See Recommended Action: Bet or pass

Input Fields Explained

Field	Description	Example
Prop Description	What you're betting	Mahomes O/U 285.5 pass yds
Prop Odds	Offered odds	-115
Implied Probability	From odds	53.49%
Your Estimate	Your projection	58%
Edge	Your advantage	+4.51%
Recommendation	Bet or pass	Bet Over

Types of Prop Bets

Player Props

Quarterback props:
- Passing yards over/under
- Passing touchdowns
- Interceptions
- Rushing yards

Running back props:
- Rushing yards over/under
- Receptions
- Longest rush
- Touchdowns

Wide receiver props:
- Receiving yards
- Receptions
- Longest reception
- Anytime touchdown

Game Props

Scoring props:
- First team to score
- First scoring method
- Total touchdowns
- Score in each quarter

Situational props:
- Successful 4th down conversions
- Total turnovers
- Penalty yards
- Sacks

Time-based props:
- First half over/under
- Will there be overtime?
- Lead changes

Alternative Lines

Spread alternatives:
Standard spread: -7 (-110)
Alternative: -3.5 (-200)
Alternative: -10.5 (+150)

Total alternatives:
Standard total: 48 (-110)
Alternative: 52.5 (+120)
Alternative: 43.5 (-150)

Implied Probability Calculation

From American Odds

Negative odds (favorite):
IP = |Odds| / (|Odds| + 100)

Example: -115
IP = 115 / (115 + 100) = 53.49%

Positive odds (underdog):
IP = 100 / (Odds + 100)

Example: +130
IP = 100 / (130 + 100) = 43.48%

Accounting for Vig

Both sides of prop:
Over -115: 53.49% implied
Under -115: 53.49% implied
Total: 106.98%

True probability:
Over: 53.49% / 106.98% = 50%
Under: 53.49% / 106.98% = 50%

Vig: 6.98% overround

Finding Value in Props

Research Factors

Player props:
- Recent performance trends
- Matchup history
- Opponent defensive stats
- Weather conditions (outdoor)
- Game script projections
- Injury status

Game props:
- Team tendencies
- Historical patterns
- Situational factors
- Referee/official tendencies

Building Your Estimate

Example: WR receiving yards

Base projection: 65 yards
Matchup adjustment: +10 (weak CB)
Game script: +5 (likely playing from behind)
Weather: -5 (wind)

Final estimate: 75 yards
Line: 72.5
Over looks valuable

Real-World Examples

Example 1: Quarterback Passing Yards

Prop: Mahomes Over 285.5 yards (-115)

Analysis:

Implied probability: 53.49%
Your estimate: Mahomes throws for 290+

Factors:
- Averaging 310 yards/game
- Facing weak pass defense (28th ranked)
- Home game (dome)
- Game script favors passing

Your probability: 60%
Edge: 60% - 53.49% = +6.51%

Recommendation: Bet over

Example 2: Running Back Rushing Yards

Prop: Derrick Henry Over 95.5 yards (-120)

Analysis:

Implied probability: 54.55%
Your estimate: Henry at 92 yards

Factors:
- Top defense allows 90 yards/game
- Short week (Thursday game)
- Team may be pass-heavy (large lead expected)

Your probability: 48%
Edge: 48% - 54.55% = -6.55%

Recommendation: Pass (or slight lean under)

Example 3: First Touchdown Scorer

Prop: WR1 to score first TD (+450)

Analysis:

Implied probability: 18.18%
Your estimate: 22%

Reasoning:
- Team targets WR1 in red zone 30%
- Expected 2.5 red zone trips
- WR1 TD probability per trip: ~35%

Edge: 22% - 18.18% = +3.82%

Small edge but +450 payout attractive

Example 4: Game Prop - Total Sacks

Prop: Over 4.5 total sacks (-110)

Analysis:

Implied probability: 52.38%
Team A averages 2.8 sacks/game
Team B averages 2.4 sacks/game
Combined: 5.2 expected

Your probability: 55%
Edge: 55% - 52.38% = +2.62%

Small edge, standard juice
Marginal bet

Prop Betting Strategy

Focus Areas

Efficiency matters:
- Research time vs edge size
- Large edges on simple props
- Avoid tiny edges after hours of work

Best value usually found:
- Lesser-known players
- Correlated props
- Cross-sport knowledge
- Local/weather knowledge

Bankroll for Props

Higher variance than spreads:
- Smaller unit sizes
- More bets, smaller stakes
- Track results carefully

Typical allocation:
Props: 0.5-1% of bankroll
vs
Main lines: 1-2% of bankroll

Correlation Awareness

Positive correlation:
- High passing yards + high completions
- Team scoring + player TDs
- Game going over + player overs

Parlaying correlated props:
Some books reduce odds for correlation
Others don't—opportunity exists

Common Mistakes

1. Ignoring Vig on Props

Mistake: Treat -115/-115 as 50/50 Problem: 6-7% vig needs overcoming Fix: Calculate true implied probability

2. Emotional Player Betting

Mistake: Bet your favorite player Problem: Bias clouds judgment Fix: Focus on data, not fandom

3. Ignoring Game Script

Mistake: Project stats without context Problem: Blowouts change player usage Fix: Factor in expected game flow

4. Over-Parlaying Props

Mistake: Large same-game parlays Problem: Correlation and vig compound Fix: Limited combinations, higher confidence

Frequently Asked Questions

Are prop bets more beatable than main lines?

Sometimes. Less efficient markets, especially for smaller players/games. But higher vig and lower limits offset this.

How much vig do props typically have?

10-15% is common (vs 4-5% on main lines). Factor this into value calculations—need bigger edges.

Should I parlay props?

Sparingly. Same-game parlays are fun but vig compounds. Only parlay strongly correlated, high-confidence picks.

How do I handicap player props?

Research: recent form, matchup stats, game script, weather, injury status. Build bottom-up projections.

Are first scorer bets good value?

Often poor value due to high vig. Unless you have strong reason to believe someone is undervalued.

What's the best sport for prop betting?

NFL and NBA have most props and liquidity. MLB pitcher props also popular. Choose where you have knowledge edge.

Pro Tips

• Account for vig: Props have higher juice

• Specialize: Deep knowledge in one area beats shallow everywhere

• Track results: Prop edges are small, need data

• Game script matters: Blowouts change everything

• Smaller units: Higher variance requires smaller bets

Related Calculators

• Implied Probability Calculator - Convert odds
• Expected Value Calculator - Bet EV
• Parlay Calculator - Multi-leg odds
• Kelly Criterion Calculator - Optimal sizing
• Sports Hedge Calculator - Hedge calculations

Conclusion

Prop bets offer opportunities beyond main lines—player performances, game events, and alternative outcomes. Our calculator converts prop odds to implied probability, helping you identify when your projections suggest genuine betting value.

Calculate Prop Bet Value Now →

The key to prop betting isn't finding exciting outcomes—it's finding where your knowledge exceeds market pricing. Our calculator quantifies that edge, showing when your research translates into positive expected value.