Profit in euros does not say whether you play well. Someone staking 100 euros who makes 500 in a year may be doing worse than someone staking 5 who makes 100. To compare you need a percentage.
The two terms
- Yieldi: net profit divided by the total amount staked. It measures what you earn for each euro you bet.
- ROI: net profit divided by the capital committed. In betting, people often say ROI when they really mean yield.
The difference shows when the same capital turns over many times. To avoid confusion, always note which formula you use.
Example
You place 200 bets of 10 euros, 2,000 euros in total. 2,080 euros come back. Net profit is 80 euros and yield is 80 / 2,000 = 4%.
How many bets are enough
At odds near 2.00 the standard deviation of one bet is about 1 unit. Over 200 bets the error of the yield is about 1 / √200 ≈ 7%. A yield of 4% is indistinguishable from luck. You need hundreds to thousands of bets for a safe conclusion.
A small early sample with positive yield does not prove an edge. A negative one does not rule it out either.