Expected Value Studio
Enter multiple outcomes with their probabilities and values. Get EV, variance, and a tornado chart that ranks which assumption matters most. Built to answer "is this bet worth it?" honestly.
Outcomes
Enter each outcome as probability,value (one per line).
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Expected value
Tornado sensitivity
Each bar shows how much the EV changes if that one probability is wrong by ±10 percentage points.
What makes this different
Most "EV calculator" pages compute a single number and stop. The interesting question is usually: which assumption, if wrong, would change my decision? The tornado chart ranks outcomes by sensitivity — the longer the bar, the more dangerous that assumption is. A bet with $10,000 EV upside and $50 EV downside might be dominated by the probability of the upside; if you're not confident in that probability, the bet isn't worth it.
Who uses it
- Decision analysts doing decision-tree reviews.
- Investors modeling position-size tradeoffs.
- Gamblers understanding variance as well as expectation.
Limitations
- Probabilities must sum to 1 (or close to it). The tool warns if not.
- EV ignores risk preference. A 1% chance of losing your house has negative EV but positive utility for some risk-seekers — and vice versa.
- No utility-curve modeling. For that, see Kelly Criterion.
Frequently asked questions
How do I use Expected Value Studio step by step without mistakes?
Follow the order given in the usage section: Compute expected value across multiple outcomes. Tornado sensitivity chart shows which assumption matters most. Includes 'is this bet worth it?' verdict. The step-by-step part matters less than the unit check that sits inside it. Confirm every unit matches the thing you are actually trying to measure before you press calculate - that single check catches more wrong answers than any other habit, and it costs about ten seconds.
What are the common mistakes when using Expected Value Studio?
Most common mistakes come down to four habits: entering 20 when the field expects 0.2 because the field is a percentage; leaving a field blank and accepting the default without checking what it stands for; changing one input and reading a result that was calculated before the change; and quoting the output as an exact figure when the page describes it as a reference estimate. Press calculate again after any edit, and treat the number as a reference point rather than a final answer.
How do I read the result from Expected Value Studio?
Read the final figure first, then come back to this section for the conditions behind it: Compute expected value across multiple outcomes. Tornado sensitivity chart shows which assumption matters most. Includes 'is this bet worth it?' verdict. Keep two things apart: the number itself, which comes from the values you typed, and the assumptions it depends on, which decide whether that number is meaningful. The page sets out what a higher or lower result means for your case, so check that direction as well as the magnitude.
Can I act on the Expected Value Studio result directly?
Treat it as one reference sheet before you decide, rather than as the answer itself: Probabilities must sum to 1 (or close to it). The tool warns if not. EV ignores risk preference. A 1% chance of losing your house has negative EV but positive utility for some risk-seekers — and vice versa. No utility-curve modeling. For that, see Kelly Criter The output describes a magnitude under the conditions you entered. It does not include what it actually costs to act, what might change while you act, or how the other side behaves. Before you commit, compare the result against reality and note which assumptions do not hold where you are.
What inputs does Expected Value Studio need?
Expected Value Studio takes 1 inputs: Number of outcomes. They are listed in the order they feed the calculation, so an earlier value can change a later one. Do not skip a field you do not recognise - work out what it means first, because a silently guessed value produces a number that looks reasonable and is not. Before typing anything, make sure every figure uses the same unit and the same time period.
What should I check before I run Expected Value Studio?
Three checks pay for themselves. First, confirm the question you need answered is really inside the scope of this tool rather than a neighbouring one. Second, confirm that the figures you have are drawn from the same source and the same period - mixing monthly and annual numbers, or two different definitions of the same quantity, quietly distorts the result. Third, keep the key inputs written down, so that later you can tell which set of numbers produced a figure you are about to quote.