Separate the stake from the profit
Odds describe what a winning selection pays under the bet’s terms. Decimal odds include the returned stake; fractional odds describe profit relative to the stake. American odds use a positive or negative reference amount.
For a $10 cash stake, these three prices are equivalent:
| Format | Price | Profit if it wins | Total returned |
|---|---|---|---|
| Decimal | 2.50 | $15 | $25 |
| Fractional | 6/4 | $15 | $25 |
| American | +150 | $15 | $25 |
The calculations assume an ordinary winning single with no deductions or special settlement. If it loses, the $10 stake is lost. A stake-not-returned free bet uses a different return calculation.
Convert the formats
Decimal total return = stake × decimal odds. Profit = stake × (decimal odds − 1).
For fractional odds a/b, decimal odds = 1 + a/b. So 6/4 becomes 1 + 1.5 = 2.50.
Positive American +150 means 150 units of profit per 100 staked. Negative American −200 means staking 200 units for 100 profit, equivalent to decimal 1.50. You can scale either calculation to a smaller stake; the reference amount is not a minimum bet.
Read implied probability carefully
For decimal odds, implied probability = 1 ÷ odds. A price of 2.50 implies 40%. This is the probability at which that price breaks even mathematically before other costs, not proof of the event’s true chance.
Suppose a two-outcome market quotes 1.90 on each side. Each implies about 52.63%; together they total 105.26%. The amount above 100% is the overround. It signals a pricing margin, not that both outcomes really have those probabilities.
Check a negative American price with a small stake
At −200, the reference is 200 units staked for 100 units of profit. For a fictional $10 cash stake, profit is $10 × 100 ÷ 200 = $5. The winning total return is $15, including the $10 stake. The equivalent prices are decimal 1.50 and fractional 1/2.
The minus sign does not mean you lose $200 or must bet that amount. It changes how the price is expressed. If the selection loses, the example loses its $10 stake. Check the accepted price on the slip before confirming; converting a price does not assess the selection itself.
Read the settlement rules too
Check the exact event and market: regulation time and “to qualify” can settle differently. Also check voids, non-runners, dead heats, deductions and maximum payouts. Rules on displaying betting terms, such as Great Britain’s betting-rule requirements, show why these contract details matter.
Keep the accepted bet slip and price. A later odds movement does not normally rewrite an already accepted fixed-odds bet, but the applicable terms govern settlement. Understanding a price helps you read the contract; it does not make a selection profitable or a loss recoverable.