Calculadora da Roleta
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
EV = aposta × (payout·P − 1)
About this calculator
The Roulette Calculator is a free online tool that calculates the probability of winning on bets in European roulette, which has 37 numbers (0 to 36). Based on the bet type, the calculator shows the actual chance of hitting and the expected value (EV) of the bet, considering the casino's payout. This helps the player understand the risk involved and the house edge.
It works simply: you select the bet type (e.g., straight up, red/black, even/odd) and enter the bet amount. The calculator uses the formula EV = bet × (payout × P − 1), where P is the probability of winning (e.g., 1/37 for a single number). The result shows the average expected value per round, which is usually negative due to the house edge of 2.7% in European roulette.
This calculator is useful for players who want to compare different bet types and understand how payout affects odds. For example, betting on a single number pays 35 to 1, but the chance is 1/37, resulting in negative EV. Outside bets (like red/black) have a payout of 1 to 1 and a chance of 18/37, with a slightly lower EV. Use the tool to plan your bankroll and avoid illusions of guaranteed profit.
Caveats: the calculator considers European roulette (single zero). In American roulette (double zero), probabilities change and the house edge doubles to 5.26%. Remember that expected value is a theoretical average; actual results may vary greatly in the short term. Never bet money you cannot afford to lose and understand that the game is based on luck, not foolproof mathematical strategies.
Frequently asked questions
What is the difference between European and American roulette for the calculator?
European roulette has 37 numbers (0 to 36), while American has 38 (additional 00). In the calculator, select the correct type; American has worse odds and a higher house edge.
Does negative expected value mean I will always lose?
No, expected value is a long-term average. In the short term, you can win or lose, but statistically the casino has the advantage.
Can I use the calculator for online roulette?
Yes, as long as the online roulette is European type (single zero). Check the game rules, as some variants may have special rules like 'La Partage' that reduce the house edge.
How does the calculator handle multiple bets?
The calculator considers one bet at a time. For multiple bets, calculate each separately and sum the expected values.
What is the house edge in European roulette?
In European roulette, the house edge is 2.7% (1/37). This means on average, the casino keeps R$ 2.70 for every R$ 100 wagered.