Use one example consistently
Our hypothetical stake is 20 units and the decimal price is 2.50. A winning total return is 20 × 2.50 = 50 units. Profit is 50 − 20 = 30 units. The returned stake is part of the 50; adding it again would double-count it.
Test the losing case too
Under a simple win-or-lose settlement, a losing selection returns zero and loses the 20-unit stake. A void, partial settlement or special offer is a different case and needs its own rules. A payout calculator should not silently assume those exceptions away.
Calculate implied probability separately
The reciprocal of 2.50 is 0.40, or 40%. This describes the probability implied by the quoted price, not a verified prediction. Our full odds guide compares equivalent fractional and American notation and shows how market margins affect the sum of implied percentages.
Check what is being priced
Before using the formula, identify the exact outcome and period. A match-winner price does not apply to an innings or player market. Settlement rules determine whether the selection qualifies as a win in the first place.
What the calculation proves
We verified the multiplication, subtraction and reciprocal using fixed inputs. The result is an accurate worked example under stated assumptions. It is not a placed bet, an actual payout or a method for choosing profitable selections. Keeping those boundaries visible is part of a useful explanation.
