Odds Calculator: Convert American, Decimal & Fractional Odds

This odds calculator converts between American, decimal and fractional odds. It also shows the gross implied probability, the total return and the net profit for a stake. The results are plain maths: they do not predict what will happen in a match.

Odds calculator and converter

Convert odds between formats and see gross implied probability, total return and net profit.

Input formatAmericanDecimalFractionalOddsStakeCalculate

American+150

Decimal2.500

Fractional3/2

Gross implied probability40.00%

Total return250

Net profit150

Try:+150-2005/21.85

The probability is a mathematical reading of the price and may include the margin. It is not a prediction of the result.

You can also use this calculator inside the ProofPitch app, in the menu under «Odds calculator».

How to use the odds converter

1. Pick the format of the number you have: American, decimal or fractional.
2. Type the odds, for example +150, -200, 2.50 or 5/2.
3. Enter the stake.
4. Read the three equivalent formats, the gross implied probability, the total return and the net profit.

A dot or a comma works as the decimal separator. In American odds type the + or - sign; in a fraction the denominator must be greater than zero.

Examples: converting American, decimal and fractional odds

With an illustrative stake of 100. These are worked examples, not current prices from any operator.

Total return includes the original stake; net profit is the return minus the stake.

Odds conversion formulas

• Positive American A: D = 1 + A / 100. For +150: 1 + 150/100 = 2.50.^[1]
• Negative American: D = 1 + 100 / |A|. For -200: 1 + 100/200 = 1.50.^[1]
• Fractional n/d: D = 1 + n / d. For 5/2: 3.50.^[2]
• Decimal to American: if D ≥ 2.00, A = +(D − 1) × 100; if D < 2.00, A = −100 / (D − 1).
• Total return = stake × D; net profit = stake × (D − 1).^[3]

Every format is first turned into decimal odds D; probability, return and profit all come from D. The American output is rounded to the nearest whole number.

Odds conversion chart

Implied probability: what it means and what it does not

Gross implied probability is 1 / D. For decimal 2.50: 1 / 2.50 = 40.00%. It is a mathematical translation of the price, not the real probability of the outcome.

In a market that covers every outcome the implied probabilities add up to more than 100% because of the bookmaker's margin, and a single price is not enough to work that margin out.^[4] That is why three numbers should be kept apart: the observed odds (a market price with source and time), the implied probability (the 1/D conversion) and the model's probability (a separate estimate that can also be wrong). ProofPitch's calculated price is a market reference plus the documented 5% margin rule; it is not an operator's quote.

Common mistakes when calculating odds

• Mixing up return and profit. At 2.50 with a stake of 100 the return is 250, but the net profit is 150.
• Dropping the sign of American odds. +200 is 3.00 in decimal and -200 is 1.50.
• Accepting decimal odds of 1 or less. Valid decimal odds are greater than 1.00.
• Reading the percentage as a forecast. It comes from the price; it does not say who will win.

Next steps

• To see how much of a price is margin, use the bookmaker margin calculator.
• With several selections on one slip, you can multiply the odds of several legs and see the return.
• If you already have your own probability, the expected value of a bet compares it with the price.
• And if you start from the profit you want, work out how much to stake for a target profit.
• New to reading odds? Start with the beginner's guide to odds and stakes. More tools: all the calculators.

Frequently asked questions

How does an odds calculator work?

It turns the format you type into decimal odds and uses that value to give the American and fractional odds, the implied probability, the total return and the net profit.

How do I convert American odds to decimal?

For positive odds divide by 100 and add 1: +150 gives 2.50. For negative odds divide 100 by the absolute value and add 1: -200 gives 1.50.

How do I convert decimal odds to American?

If the decimal is 2.00 or higher, subtract 1 and multiply by 100. If it is lower than 2.00, divide −100 by D − 1.

How do I convert fractional odds to decimal?

Divide the numerator by the denominator and add 1. 5/2 becomes 3.50.

How do I calculate implied probability from odds?

Divide 1 by the decimal odds. At 2.50 the implied probability is 40.00%. It can include the bookmaker's margin.

How do I work out my profit on a bet?

Multiply the stake by D − 1. With a stake of 100 at 2.50: 100 × 1.50 = 150 net profit.

Does the converter recommend a bet?

No. It only converts formats and does arithmetic with the numbers you enter.

If you need the basics of return, profit and negative odds first, read what odds mean and how they work.

18+. Take part only where it is legal. Betting carries a risk of loss. Do not treat potential returns as a budget and do not chase losses. If gambling stops being under control, stop and look for help from the support services in your country.

Notes and sources

1. Pinnacle. How to convert between Decimal & American odds. Checked on 05/11/2026.
2. Pinnacle. Fractional odds vs. Decimal odds. Checked on 05/11/2026.
3. Betfair. How do odds work?. Checked on 05/11/2026.
4. Pinnacle. Margin Calculator. Checked on 05/11/2026.