How the formats map

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• Fractional odds remain useful for comparison and historical references.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 conversion helps

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.

1. Choose the format you are starting from.
2. Enter the quote exactly as shown in that system.
3. Check the implied probability and the other translated views.
4. Use the stake outputs to make the comparison tangible.

A $0.40 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.

Mistakes to avoid

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

Best comparison habit: 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.