FREE / NO REAL MONEY
Parlay / SGP Insurance EV Calculator
Model a parlay-insurance promotion where the refund triggers only if exactly one leg loses. Compare cash and bonus-bet refunds, caps and conversion value.
How it works & examplesUnderstand the calculation
How parlay insurance EV is calculated
With n identical independent legs and per-leg win probability q, all-win probability is q^n. Exactly-one-loss probability is n × (1 − q) × q^(n − 1).
Insurance on one failed leg only has meaning against the original multi-leg payout; compute that ticket in Parlay Calculator: Combined Odds & Payout.
Baseline expected P/L uses the all-win probability: q^n × stake × parlay odds − stake. Insurance EV adds exactly-one-loss probability × cash-equivalent refund.
Probability of two or more losses is 1 − all-win probability − exactly-one-loss probability. Those outcomes receive no refund in this model.
Exactly-one-loss probability is especially sensitive to dependence between legs. Treat the independent-leg output as a baseline scenario, then stress-test higher or lower joint dependence for same-game legs before using the insurance value as a decision metric.
Maths & verification
Calculate the probability of exactly one losing leg and the expected value of a parlay or SGP insurance refund.
Try the simulator below. Input values stay in your browser; no account or money is involved.
Model assumptions: No. Virtual games use declared teaching models. Verify any actual operator’s payout rules independently.
Related interactive tools
- Parlay Calculator: Combined Odds & Payout
Multiply 2–10 decimal odds, calculate parlay payout, implied probability and hypothetical expected value using independent-leg assumptions.
- No Sweat Bet / Bet Insurance EV Calculator
Calculate the expected value of a loss refund, including cash vs bonus-bet refund, cap, refund percentage and bonus-credit conversion rate.
- Bonus Bet / Bet Credit Conversion Calculator
Calculate hedge stake, guaranteed cash-equivalent value and conversion percentage for stake-not-returned or stake-returned bonus bets.
- Odds Boost / Profit Boost EV Calculator
Calculate boosted decimal odds, capped extra winnings, break-even probability and expected value from your own win-probability estimate.
How to use the tool
Measure the value of parlay insurance when the promotion refunds only an exactly-one-leg miss.
- Enter stake, total parlay decimal odds, number of legs and your estimated average independent win probability per leg.
- Set refund percentage, cap and whether the refund is cash or bonus credit with a conversion rate.
- Compare all-legs-win probability, exactly-one-leg-loss probability, baseline EV, expected refund value and insured EV.
Understanding your result
For 4 independent legs each estimated at 70%, the probability all four win is 0.7^4 = 24.01%. The probability exactly one loses is 4 × 0.3 × 0.7^3 = 41.16%. A 100 refund converted at 70% therefore has expected promo value 0.4116 × 70 = 28.81.
Scope and limitations
The independence assumption is a model. SGP legs can be correlated, sportsbooks may exclude certain legs, pushes and voids can alter qualification, and real refund rules can differ.
Before you rely on the result
- How the calculation works
Formulas, assumptions, rounding and model limits are documented on the methodology page.
- Check the current inputs
Use the odds, RTP, fees, bonus terms or other values currently shown by the operator or market.
Parlay insurance calculator: one-leg miss probability and refund EV
Parlay insurance is structurally different from a normal losing-bet refund because the promo may trigger only when exactly one selection loses.
The expected value therefore depends on the probability distribution across leg outcomes, not just on the chance that the whole parlay loses.
Exactly-one-loss probability can be larger than all-win probability
For four 70% legs, all-win is 24.01% while exactly one loss is 41.16%. That is why a one-leg-miss refund can carry substantial promo value.
More legs change both win and refund probabilities
Adding legs reduces all-win probability quickly, but exactly-one-loss probability first rises and can later fall depending on q. The promo value is therefore not monotonic in leg count.
SGP correlation is the main model limitation
Same-game selections are often positively or negatively correlated. Using independent identical leg probabilities is transparent and useful for scenarios, but it is not a sportsbook pricing model.
Questions about this calculation
Why exactly one loss instead of any loss?
Many parlay-insurance offers trigger only when every leg but one wins. Losing two or more legs usually produces no refund.
Why can SGP insurance be harder to model?
Same-game legs can be correlated, so multiplying identical independent probabilities may materially misstate both all-win and one-miss chances.
When is Parlay / SGP Insurance EV Calculator the right tool?
Measure the value of parlay insurance when the promotion refunds only an exactly-one-leg miss.
How should I read the result from Parlay / SGP Insurance EV Calculator?
For 4 independent legs each estimated at 70%, the probability all four win is 0.7^4 = 24.01%. The probability exactly one loses is 4 × 0.3 × 0.7^3 = 41.16%. A 100 refund converted at 70% therefore has expected promo value 0.4116 × 70 = 28.81.
What can Parlay / SGP Insurance EV Calculator not tell me?
The independence assumption is a model. SGP legs can be correlated, sportsbooks may exclude certain legs, pushes and voids can alter qualification, and real refund rules can differ.