Two possible payoff trays and a separate small entry-cost token. Original AI-generated artwork produced for GreenCalc; not a measured diagram or empirical data display.
Put every outcome on the same accounting basis
An expected-value table should use comparable net outcomes. If a hypothetical game costs 10 units to enter and pays a gross return of 30 units on success, the success net outcome is +20, not +30. If failure pays nothing back, the failure net outcome is −10. Subtracting the entry cost only from losing outcomes overstates the mean.
Calculate a complete payoff distribution
Suppose success has probability 30% and failure has probability 70%. Enter outcome −10 with probability 70, and outcome 20 with probability 30, in the Expected Value Calculator. The expected net outcome is (−10)(0.7)+(20)(0.3) = −1 unit. The variance is 189 squared units and the standard deviation is approximately 13.7477 units.
| Outcome | Net amount | Probability |
|---|---|---|
| No gross return | −10 | 70% |
| Gross return 30 | +20 | 30% |
Do not subtract the same cost twice
If every row already contains a net amount after the entry fee, do not subtract the fee again from the computed expectation. If you use gross return rows instead, a fixed fee can be subtracted once from the gross expected value. Both approaches agree when applied consistently. Variable fees, refunds and conditional costs must follow the relevant outcome rather than being treated as a universal fixed amount.
Separate the mean from the decision
An expected loss of one unit is an average under the entered model, not a prediction that a single play loses exactly one. Whether a hypothetical decision is acceptable also depends on risk, limits and the validity of the probabilities. This tool does not supply investment forecasts or personal betting advice. Read same expectation, different risk before comparing alternatives solely by their mean. For quoted odds rather than a payoff table, the Implied Probability Calculator has a separate conversion purpose.
Check the model behind your result
Use the Expected Value Calculator for the supported calculation and review its stated assumptions before interpreting the output. Find related tools in the Statistics category, or browse the GreenCalc homepage for other calculation topics.
By GreenCalc Editorial Team · Updated 2026-10-26