Probability to Odds Converter
PREDICTION MARKETS · LIVE KALSHI PRICES OR MANUAL ENTRY
Convert a probability — or a live prediction market price — into decimal odds, American odds, and breakeven win rate.
Or paste any Kalshi ticker via the API — this dropdown is just a few examples.
Live prices come from Kalshi's public market-data API (a CFTC-regulated exchange) — a market's price in cents is already its implied probability. The vig only shows up when using a live market, since it needs both the YES and NO price.
What's the probability?
Pick a live prediction market or enter your own estimate — I'll show the odds format traders actually use.
What is a probability-to-odds conversion?
A prediction market price is already a probability — Kalshi's contracts settle at $1 or $0, so a price of $0.35 means the market thinks the event is 35% likely. Traders and sportsbooks, though, usually talk in decimal or American odds, not raw probability. This converts between the two, and — when the input is a live market — separates out the vig (the exchange's own built-in edge) from the underlying probability.
The formulas
- decimalOdds = 1 / probability
- americanOdds = probability ≥ 0.5 ? −100 × p / (1 − p) : 100 × (1 − p) / p
- breakevenWinRate = probability × 100
- vig = (yesPrice + noPrice − 1) × 100 — only computable with both sides of a live market
Worked example
A market prices an event at 25% (probability 0.25):
- decimalOdds = 1 / 0.25 = 4.00
- americanOdds = 100 × 0.75 / 0.25 = +300
- breakevenWinRate = 25%
You'd need to be right more than 25% of the time for a bet at this price to break even — that's the whole point of converting to a win-rate number instead of staring at odds.
Where the live prices come from
Kalshi is a CFTC-regulated exchange with a public, keyless market-data API. Its crypto category prices BTC/ETH/SOL and other coins' year-end and threshold outcomes directly. This tool reads that live price — it doesn't estimate or invent a probability.
Where to go next
Want to see the market's full implied view of where BTC/ETH ends the year, not just one threshold? Use Market-Implied Odds. Think your own probability estimate beats the market's? Size the bet with the Edge Sizer.
Use via API or MCP
This calculation is available as a deterministic API call — useful for bots or AI agents normalizing prediction-market prices into a common odds format.
How is a market price the same thing as a probability?
Kalshi contracts settle at exactly $1 (YES) or $0 (NO). A contract trading at $0.35 means the market collectively prices the event at 35% likely — that's the definition of an efficient binary market's price.
What is the "vig" and why can't I see it with a manual probability?
The vig is the exchange's built-in edge — the amount by which the YES and NO prices sum to more than $1. Computing it needs both sides' prices, which only a live market snapshot has; a manually entered probability is just one number with no counter-side to compare against.
Why do American odds sometimes show a plus and sometimes a minus?
By convention, probabilities at or above 50% show negative American odds (you risk more than you win), and probabilities below 50% show positive odds (you win more than you risk) — the same convention sportsbooks use.
Does this only work for Kalshi crypto markets?
The live-lookup mode is scoped to Kalshi's crypto-price category (BTC/ETH/etc.) for now. The manual-probability mode works for any probability from anywhere — it's pure math, not tied to one venue.