A 4% profit over 500 bets feels like proof. It isn’t. This free luck vs skill calculator tells you how often a bettor with no edge at all would post a record like yours, and how many more bets you’d need before luck stops being a good explanation.
Luck vs skill: the size of the swing
At even money, one bet’s profit swings by about one stake either way. Over n bets your ROI swings by roughly 1 ÷ √n, and higher odds make it swing more. At average odds of 2.10, 500 bets give a luck swing of about ±4.7% ROI, one standard deviation. So a +4% record is less than one swing from break-even. A punter with no skill gets there about one time in five.
Take the same +4% ROI over 3,000 bets and the swing shrinks to ±1.9%. Now luck alone does it only about 2% of the time. That’s a record worth taking seriously.
How many bets do you need?
The calculator shows the number of bets for 95% confidence at your ROI and odds. Two things push it up fast:
- Thin edges. Halve your ROI and you need four times as many bets.
- Long odds. A bet at 6.0 swings more than twice as much as one at evens, so at the same ROI a tipster on big prices needs about five times as many bets.
To test yourself against a typical punter rather than against breaking even, set the no-edge result to −4% or −5%, roughly what the bookmaker’s margin costs someone picking at random.
What the test can’t fix
It assumes level stakes and an honest, complete record. Picking your best 500 bets after the fact, or switching sports when one goes cold, makes any record look better than it is. Closing line value, whether your odds beat the final price, is a faster check that you’re beating the market; the profit takes much longer to prove.
Work out your strike rate first with the win percentage calculator, track bets in the bet tracker, and size stakes with the Kelly criterion calculator.
Play for fun with money you won’t miss. If you’re spending more than you planned, BeGambleAware.org is free and confidential.