Prediction Market Calculator
A binary prediction market has two opposing contracts whose prices always sum to $1.00. Use this calculator to see how a contract’s price maps to an implied probability, and what a position pays out if your side wins or loses.
CALCULATOR
USA vs Spain — FIBA World Cup
Adjust the price using any of the three controls below to see how it affects probability and payout.
USA: $0.65
65% implied probability
1.54 decimal odds
Spain: $0.35
35% implied probability
2.86 decimal odds
Both contracts always sum to $1.00 (100%).
If USA wins
- Contracts
- 153.85
- Payout
- $153.85
- Profit
- +$53.85
If USA loses
- Payout
- $0.00
- Loss
- -$100.00
Implied probability
65%
The market believes USA has a 65% chance of winning.
How to use it
- Pick a contract. Switch between the two outcomes with the team buttons. The selected contract is the one the price display and payout scenarios describe.
- Set the price three ways. Drag the slider, click or drag along the scale bar, or type a value into the price field — all three stay in sync, because a contract price is the implied probability (a $0.65 price means a 65% chance).
- Enter how much to spend. The payout boxes update in real time: how many contracts you buy, what you collect if your side wins, and what you lose if it doesn’t.
- Watch the other side. The opposing contract’s price always fills the gap to $1.00 — that’s the core invariant of a binary market.
Related lessons
- What is a prediction market? — The foundational lesson this calculator accompanies: what you trade, how price works as probability, and what happens when an event resolves.