Bet Builder Calculator

Multi-Bet Analysis Tool

Build and analyze your entire bet slip with our free bet builder calculator. Add multiple individual bets and see the combined expected value, total risk, weighted average edge, and overall ROI analysis. Unlike a parlay calculator which combines bets into one dependent wager, this tool analyzes independent bets as a portfolio.

📊 How This Tool Works

Enter each bet's odds, your estimated true probability, and stake amount. The calculator shows individual expected value for each bet, then combines everything to give you portfolio-level analysis including total EV, weighted average edge, and overall ROI. This helps you understand the complete mathematics of your betting activity.

📝 Your Bet Slip

Add bets below. For each bet, enter the odds offered by your sportsbook and your estimated true probability of winning.

Understanding Bet Slip Analysis

Professional bettors don't look at individual bets in isolation—they analyze their entire betting portfolio. The mathematics of expected value applies to your complete betting activity, not just single wagers. This bet builder helps you think like a professional by calculating combined expected value across all your selections.

Why Analyze Multiple Bets Together?

According to research from the UNLV International Gaming Institute, recreational bettors typically make 5-15 bets per week. Understanding the combined mathematics helps you:

  • Identify overall profitability: One +EV bet might be offset by multiple -EV bets
  • Optimize stake allocation: See how your money is distributed across different edge profiles
  • Track true performance: Weighted average edge shows your actual expected return per dollar
  • Make informed decisions: Decide which bets to place and which to skip

Key Metrics Explained

Combined Expected Value (EV)

Combined EV is simply the sum of individual expected values for each bet. If your bet slip has three bets with EVs of +$5.50, -$2.00, and +$3.25, your combined EV is $6.75. This represents your expected profit (or loss) if you made these same bets repeatedly over time, based on the mathematics described by Britannica's probability theory.

Weighted Average Edge

Simple average edge treats all bets equally, but you might stake $100 on one bet and $20 on another. Weighted average edge accounts for stake sizes:

Weighted Edge = Σ(stake × individual edge) / total stake

This gives a true picture of your expected return per dollar wagered across all bets.

Expected ROI (Return on Investment)

Expected ROI is your combined expected value divided by total stake, expressed as a percentage. A +5% ROI means you expect to profit $5 for every $100 wagered. As the American Gaming Association notes, most recreational bettors have negative expected ROI due to the built-in sportsbook margin.

Common Bet Slip Scenarios

The Recreational Bettor

A typical recreational bet slip might show 5 bets with an overall -4.5% weighted edge. This means for every $100 wagered, the expected loss is $4.50. This is the cost of entertainment—similar to buying a movie ticket. Our gambling cost comparison calculator helps put this in perspective.

The Sharp Bettor

Professional bettors target slight positive edges—typically 2-5%. A bet slip showing +2.8% weighted edge with proper bankroll management represents a sustainable long-term approach. Even small edges compound over thousands of bets.

The Mixed Approach

Many informed bettors mix entertainment bets (accepted -EV) with attempted value plays. The bet builder helps separate these by showing exactly which bets contribute positive vs. negative EV to the overall slip.

Improving Your Bet Slip Edge

  1. Shop for better odds: Use our odds comparison calculator to find the best price
  2. Calculate true probability carefully: Overestimating creates false +EV—be conservative
  3. Cut -EV entertainment bets: Each one drags down your overall expectation
  4. Allocate stake to edge: Put more money on higher-edge opportunities
  5. Track over time: Use our session tracker to compare actual vs. expected results

Frequently Asked Questions

What's the difference between this and a parlay calculator?

A parlay calculator combines multiple selections into one bet where all must win. The bet builder analyzes independent bets—each settles separately. You could win 3 of 5 bets in a builder slip; in a 5-leg parlay, that's a complete loss. The mathematics are fundamentally different.

How do I estimate true probability?

Estimating true probability requires research, historical data analysis, and experience. Start with the implied probability from the odds, then adjust based on your analysis. If you think the market is efficient, your true probability estimate should be close to implied probability (meaning near-zero edge). Be conservative— overestimating probability creates false +EV readings.

Why does the tool show negative EV bets?

Most recreational bets have negative expected value due to sportsbook margins. Showing this isn't discouragement— it's education. Many people gamble for entertainment, fully aware of the cost. The bet builder helps you understand exactly what that entertainment costs mathematically, so you can make informed decisions.

Should I bet more on higher edge opportunities?

The Kelly Criterion suggests betting proportionally to your edge. However, this assumes your probability estimates are accurate—which they rarely are. Most professionals use fractional Kelly (25-50% of full Kelly) to account for estimation error. The bet builder helps visualize how different stake allocations affect your overall expected return.

Can I have overall +EV with some -EV bets?

Yes. If you have one bet with +$20 EV and two bets with -$5 EV each, your combined EV is +$10. However, this assumes your +EV estimate is accurate. Professional bettors typically avoid -EV bets entirely since each one erodes overall expectation. The bet builder helps visualize which bets are helping vs. hurting your bottom line.

How reliable are these EV calculations?

EV calculations are only as reliable as your probability inputs. The math is exact, but "garbage in, garbage out" applies. If you estimate 55% probability but the true probability is 48%, your "positive EV" is actually negative. Consider stress-testing by reducing your probability estimates by 2-5% to see how sensitive your conclusions are to estimation error.

What's a good weighted edge target?

Sportsbooks operate with 3-10% margins depending on the market. Achieving consistent +2-5% weighted edge is considered excellent and is what professional bettors target. Anything above +10% should make you question your probability estimates—edges that large are rare and usually indicate estimation error rather than genuine opportunity.

Related Calculators

Disclaimer: This calculator is for educational purposes only and does not constitute gambling advice. Expected value calculations depend on the accuracy of your probability estimates—actual results will vary due to variance. Never gamble with money you cannot afford to lose. If gambling is affecting your life negatively, please seek help from BeGambleAware or contact the National Council on Problem Gambling. For more resources, visit our responsible gambling page.