Roulette odds calculator: European bet probabilities

h2>How to use the roulette odds calculator

Select a bet position. Click or tap a number, an inside-bet position, or an outside selection such as red or the first dozen. A marker records the selection.
Add any other selections. You can combine bets. Selecting the same position again does not add a larger stake; this tool records whether a position is selected.
Press Calculate. Read the percentage for the current selection. After adding or removing a bet, press Calculate again to obtain a result for the revised layout.
Use Undo or Clear bets. Undo removes the most recently added selection. Clear bets removes all selections so you can start a fresh comparison.

The tool uses a 37-pocket wheel with numbers 1 to 36 and one zero. Its percentage assumes each pocket is equally likely on a spin. No deposit or real-money wager is involved in using the calculator.

Where to select each bet

Use the layout positions below to build a selection. For a detailed explanation of chip placement and individual payouts, open our roulette bets guide.

Bet	Position on the layout	Numbers covered
Straight up	The center of one numbered cell, including 0	1
Split	The shared border between two adjacent numbered cells	2
Street	The outside edge of a row of three numbers	3
Corner	An interior intersection shared by four numbered cells	4
First four: 0, 1, 2, 3	The outside junction between zero and the first numbered row	4
Six line / double street	The outside intersection between two adjacent rows of three	6
Dozen	1–12, 13–24, or 25–36	12
Column	The 2:1 position at the bottom of a column	12
Red, black, odd, even, low, or high	The matching outside position; low is 1–18 and high is 19–36	18

What the percentage means

The calculation is distinct covered numbers ÷ 37 × 100. A straight-up bet covers one number and returns 2.70%. Red covers 18 and returns 48.65%. These are probabilities rounded to two decimal places.

For combinations, the calculator counts the union of the selected numbers. Each pocket appears once in that count, even when several bets cover it. Adding a second bet can leave the result unchanged if all of its numbers were already covered.

Examples to try

Press Clear bets before each example, add the listed selections, and press Calculate.

Selection	Distinct numbers covered	Expected result	How to interpret it
Number 17	1	2.70%	One possible winning number out of 37
Red	18	48.65%	Any of the 18 red numbers produces a winning bet
Red + number 1	18	48.65%	Number 1 is already red, so it adds no new covered pocket
Red + number 2	19	51.35%	Number 2 is black and adds one covered pocket
Red + first dozen	24	64.86%	Six red numbers belong to the first dozen and are counted once
Red + black	36	97.30%	Zero remains uncovered; the figure does not establish a profitable round
Red + black + number 0	37	100.00%	Every pocket produces at least one winning bet, while the total return still depends on the stakes and payouts

Why a high percentage can still leave a loss

Suppose you place $1 on red and $1 on black at a standard European table. A red or black result returns $2 from the winning bet against a $2 total stake, so the round breaks even. Zero loses both bets. The 97.30% coverage figure describes the chance of receiving a payout, while the chance of a net profit for that equal-stake combination is zero.

Adding $1 on zero takes the coverage to 100% and the total stake to $3. A red or black result returns $2, leaving a $1 loss. A zero returns $36 from the straight-up bet, leaving a $33 profit. All pockets are covered, yet 36 of the 37 outcomes still produce a net loss in this example.

Net result = total money returned − total money wagered. To calculate it, you need the amount on every bet and the payout for each possible winning result. The calculator’s coverage percentage contains neither of those amounts.

What to check before using a result

Wheel: the calculator uses European single-zero roulette. An American wheel has 38 pockets, so this percentage does not apply.
Selections: check which numbers your bets cover, especially where two bets overlap.
Calculation: run Calculate after changing the layout so the displayed result corresponds to the current selection.
Paytable: any real game may have special zero rules, side bets, fees, or multipliers. The tool does not model those features.
Time frame: the result describes one spin. It does not predict the next number, a session profit, or the chance of losing a whole bankroll.

Under the standard European paytable, ordinary bets retain a 2.70% house edge. Covering more numbers changes how often a bet can pay and how the round’s returns are distributed. It does not erase the average loss built into those payouts. The UK Gambling Commission explains house edge as an average share of stakes retained over time.

For expected value and the limits of betting systems, read our mathematical roulette strategy analysis. Our roulette tutorial covers the basic rules, and the live roulette strategy guide covers table selection and session limits. Use the calculator to understand a selection before risking money, and keep any gambling within an amount you can afford to lose.

What does the roulette odds calculator percentage show?

It shows the chance that at least one selected bet wins on a fair 37-pocket European wheel. The calculation counts each covered number once. It does not calculate the chance of a net profit after all stakes.

Can I use this calculator for American roulette?

No. This calculator uses one zero and 37 pockets. American double-zero roulette has 38 pockets, so a red bet has probability 18/38, or 47.37%, instead of 18/37, or 48.65%. Use the correct wheel and the specific game rules for any calculation.

Why does adding a bet sometimes leave the result unchanged?

The new bet may cover only numbers already included in your selection. For example, red already covers number 1. Adding a straight-up selection on 1 leaves 18 distinct pockets covered, so the result remains 48.65%.

Does 100% coverage guarantee a profit?

No. It means every pocket produces at least one winning bet. Other bets can lose on the same spin. With $1 each on red, black, and zero, a red or black result returns $2 against a $3 total stake, leaving a $1 loss under standard payouts.

Can I enter different stake amounts?

The current calculator records selected positions without accepting wager amounts. Clicking an already selected position does not increase its stake. Use the result to compare covered numbers; calculate cash returns separately from the actual stakes and paytable.

Can the calculator predict the next roulette number?

No. It calculates probability from the numbers selected on the layout. Under the fair, independent-spin model, previous results do not change the probability on the next spin. A high coverage percentage does not make a particular number due.

Roulette Odds Calculator