Decimal odds include the stake
Multiply stake by decimal odds to calculate a winning total return. Subtract the original stake to calculate profit. With a hypothetical 20-unit stake at 2.50, total return is 50 units and profit is 30 units. A losing selection returns nothing under this simple example; special settlement rules are outside the calculation.
Fractional odds express the profit ratio
Fractional odds of 3/2 mean three units of profit for every two units staked on a winning selection. Convert them to decimal by calculating 3 ÷ 2 + 1 = 2.50. The extra one represents the returned stake. This is the same price as the decimal example, not a different payout opportunity.
American odds use two conventions
Positive +150 means 150 units of profit on a 100-unit winning stake, equivalent to 2.50 decimal. Negative −200 means a 200-unit winning stake yields 100 units of profit, equivalent to 1.50 decimal. The signs describe the convention; they do not mean positive or negative certainty.
Implied probability is a calculation from price
For decimal odds, divide 1 by the price and multiply by 100. At 2.50 that gives 40%. It is a price-derived figure, not an independently measured probability. In a two-outcome illustration where both prices are 1.90, the two implied percentages total about 105.26%, showing why adding quoted prices does not necessarily produce a fair 100% model.
Check the arithmetic, then check the scope
We recalculated these examples with fixed inputs and matched the equivalent formats. The result validates the arithmetic only. For a simpler worked walkthrough see decimal odds explained. For what makes the selection win, lose or become void, read market settlement rules. A correct payout formula cannot repair a misunderstood market.
