helpmedecide

Expected value calculator.

Not every decision is about money. Map out the outcomes, guess the odds, and let the math whisper what your gut already suspects.

How it works01
  1. 1
    Name your decision — What are you considering doing?
  2. 2
    Map the outcomes — What could realistically happen?
  3. 3
    Rate each outcome — How would it feel, from −100 (devastating) to +100 (life-changing joy)?
  4. 4
    Estimate the odds — What's the rough probability of each outcome?
  5. 5
    Read your Expected Value — A positive number means the decision likely pays off emotionally over time.
The decision02
The outcomes03

What could actually happen?

For each outcome: a value from −100 to +100 (how it would feel), and a percentage — all rows add up to 100.

The answer04

Expected Value

+13.3A nice boost

High variance — proceed with caution

The expected value is positive, but the outcomes are spread wide. Each attempt has a 67% chance of a positive result, and you'd need approximately 31 repetitions before the positive EV reliably shows up (95% confidence). That means any single try is a real gamble. If you can't repeat this decision many times, the EV is technically on your side but the ride could be rough.

Contribution breakdown05
Best case scenario
+70 × 33% = +23.1
Most likely outcome
+10 × 34% = +3.4
Worst case scenario
-40 × 33% = -13.2
Net EV
+13.30
How to think about this06

Positive EV means proceed.

Positive EV means proceed. A positive expected value means that if you were to face this decision many times over, you'd come out ahead emotionally. That's worth something.
Negative EV means think twice. It doesn't mean don't do it — sometimes negative EV decisions are the right ones. But you should know you're fighting the math, not riding it.
EV is not certainty. You're rolling the dice once, not a thousand times. A positive EV decision can still go wrong.
On loss aversion: Feelings aren't dollars. Research shows losses feel roughly twice as painful as equivalent gains feel good. Consider doubling your negative values to account for how losses actually land — it often shifts the picture meaningfully.
Related essays99

From the notebook.

May 8, 2025

How Many Times Before the Math Pays Off?

A positive expected value doesn't mean you'll win on the first try. Here's how to tell whether one shot is enough — or whether you need to keep swinging.

April 1, 2025

Why the Best Decisions Feel Scary

The decisions with the highest expected value often feel the most terrifying. Here's why that's actually good news.

March 12, 2025

The Math Behind Your Gut Feeling

Your gut isn't irrational — it's doing expected value math, just badly. Here's how to do it well.