Roulette Probability Calculator: Your Chance of Hitting in N Spins
Pick a wheel, a bet and a number of spins to see the exact chance of winning at least once, or at least a set number of times. No simulation, just the binomial formula.
Want the full list of bets and payouts? See the
, or work out how likely a run of the same colour is with the
The short version
A single number on a European wheel hits one spin in 37 (2.7%). Even after 37 spins the chance of having hit it at least once is only about 64%, not 100%.
The chance of at least one win in n spins is 1 − (1 − p)ⁿ. For a single number you need about 26 spins for a 50% chance, 85 for 90% and 169 for 99%.
Every standard bet on a wheel carries the same house edge, 2.70% European and 5.26% American, so a bet that wins more often simply pays less when it does.
Past spins never change the next one. A number that has not hit in 100 spins is exactly as likely as any other on the next spin.
How the odds work
The formula
Each spin is independent, so the chance of losing n spins in a row is (1 − p)ⁿ, where p is the chance of winning one spin. Subtract that from 1 and you have the chance of winning at least once. For more than one win the calculator adds up the exact binomial probabilities instead.
Why 37 spins does not guarantee a hit
People often assume a 1-in-37 chance means "due" after 37 spins. It does not. The chance of missing all 37 is (36/37) to the 37th power, about 36%, so roughly one player in three will not see their number in that many spins.
Better odds do not mean a better bet
Red or black wins nearly half the time and a single number a tiny fraction, but payouts are set so each pays back the same share in the long run. The house keeps 1 pocket in 37 on a European wheel and 2 in 38 on an American one, whichever bet you choose.
Wins in a row are a different question
This page counts wins anywhere in a set of spins. If you want the chance of a run in a row, such as ten reds, that is a separate calculation, and the streak calculator on this site does it exactly. Everything here is educational, with no real money involved.
Table Edge