Calculator
Use this when you are moving between prediction market prices and other odds formats instead of trying to do mental conversion on the fly. It is especially helpful when your model outputs probabilities but the comparison market uses American or decimal odds.
Source quote
This converter assumes a standard binary contract that settles at $1.00 when the event happens and $0.00 when it does not.
How odds formats map together
A binary prediction market price is an implied probability expressed on a zero-to-one scale. A price of $0.40 means the market is implying roughly a 40% chance of the event happening before fees and frictions are considered.
Decimal, American, and fractional odds express the same idea in different language. The converter exists so you can compare these formats cleanly when your inputs come from different markets, books, or modeling tools.
- Prediction price and implied probability are the most direct view.
- Decimal odds are common in many sportsbooks and models.
- American odds are common in US betting interfaces.
- Fractional odds remain useful for comparison and historical references.
When to use an odds converter in practice
Use a converter whenever the price source and the evaluation framework speak different languages. That often happens when a trader compares a prediction market contract with sportsbook lines, model output, or a spreadsheet that expects decimal odds.
It also helps prevent small conversion mistakes that can distort edge analysis. A trade that looks attractive under one incorrectly converted format can disappear once the price is translated correctly.
- 1Choose the format you are starting from.
- 2Enter the quote exactly as shown in that system.
- 3Check the implied probability and the other translated views.
- 4Use the stake outputs to make the comparison tangible.
Worked odds example
Suppose a prediction market contract trades at $0.40. The converter shows that this maps to about 40% implied probability, decimal odds of 2.50, American odds of +150, and fractional odds of 3/2. That makes it much easier to compare with an external line that may not be quoted in price form.
Adding a stake input then shows the return and profit you would expect under that equivalent price. This is useful when you want a fast intuition check before moving to EV or sizing analysis.
- The same quote can look very different depending on format.
- Stake-based profit makes the conversion easier to interpret quickly.
- Accurate format conversion reduces avoidable edge-analysis errors.
Common conversion mistakes traders make
One common mistake is forgetting that prediction market price is already probability-like, which leads to accidental double conversion. Another is misreading American odds signs, especially when switching between favorites and underdogs quickly.
Fractional inputs also cause avoidable errors when the ratio is typed incorrectly or mentally simplified the wrong way. Using a converter removes that friction and keeps later EV work cleaner.
- Double-converting an already probabilistic market price
- Misreading positive versus negative American odds
- Typing fractional odds incorrectly
- Comparing formats without checking the implied probability underneath
When two markets look different, reduce both to implied probability first. That is the clearest way to see whether there is any real price disagreement to investigate.
Sources
These references support the assumptions and workflow guidance on this page. Always verify current platform rules before relying on a calculator preset.
Internal primer on how binary contract prices map to implied probability.
Internal comparison page that benefits from translating prices into familiar betting formats.
Internal guide on comparing market prices against fair probability estimates.