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StakeSmith field notes04 / PARLAY MATH

PARLAY MATH

Parlay math. Payout is only half the story.

Looking for a parlay analysis tool? Start with the difference between what a ticket pays and how often it would need to win. Then inspect the numbers behind an NFL blueprint.

Inspect a parlay in the Forge

WORKED EXAMPLE / TWO LEGS AT -110

Two favorites do not make a sure thing.

Suppose two independent legs are each priced at -110. Each converts to 1 + 100 / 110 = 1.9091 decimal odds. Multiplying the prices gives 3.6446 combined decimal odds. A $10 stake returns $36.45 if both win, including the original $10. Net profit is $26.45.

Now assume a fair 50% chance for each leg. Both win with probability 0.50 × 0.50 = 25.00%. The price requires a 27.44% win rate to break even. Under these assumptions, expected value is negative even though a winning ticket more than triples the stake.

ILLUSTRATIVE TICKET / $10 STAKE

Leg A / -110
50% assumed
Leg B / -110
50% assumed
Total return
$36.45
Net profit
$26.45
Both win
25.00%

-8.88% expected value

Illustrative example, not a prediction. EV = probability × decimal payout − 1. At this $10 stake, the expected net result is -$0.89 per hypothetical ticket. That is an average under the model, not the result of a single bet.
01 / CHECK THE PRICE

Keep return and profit separate.

Compare the actual sportsbook quote with your calculation. Boosts, voids, pushes and settlement rules can change a return. A multiplied decimal price is an illustration, not a sportsbook payout promise.

02 / CHECK THE ASSUMPTIONS

Count the ways the estimate can fail.

The 50% inputs here are assumptions, not probabilities derived from these prices. Correlated legs need a joint estimate. Review source data, bookmaker margin and warnings in the Forge; a displayed estimate does not verify an edge.

03 / REVIEW A BLUEPRINT

Put the math beside the legs.

Open the NFL Forge to review a blueprint's odds, estimated probability and EV together. Generation needs available data providers. Google sign-in is required to save a blueprint. No wager is placed by reviewing or saving one.

Test an estimate before trusting it.

A calculated EV is only as useful as its inputs. See how changing a win estimate affects a result in the strategy testing walkthrough. If your question is how much to stake from your own estimate, use the Kelly calculator.

THE DETAILS

Before you decide.

How do you calculate a parlay payout?

For a standard all-win parlay, convert each American price to decimal odds and multiply the decimals. Stake times combined decimal odds is total return, including the stake. Subtract the stake for net profit. Actual sportsbook rules and prices may differ.

Is implied probability the chance of winning?

It is the break-even probability implied by a price, not a verified forecast. Bookmaker margin and the quality of your probability estimates matter. A larger payout does not establish a positive expected value.

Can I multiply probabilities for a same-game parlay?

Only independent outcomes support simple probability multiplication. Same-game legs can be correlated, so their joint probability needs a model that accounts for that relationship. This example does not model correlation.

What can I inspect in StakeSmith?

The NFL Forge presents blueprint legs, odds-based probability and expected-value estimates when data providers are available. Review the assumptions and warnings before deciding. StakeSmith does not accept or place wagers.

21+. Educational and entertainment use. Estimates depend on assumptions. You may lose money. StakeSmith does not accept or place wagers.