Zero RouletteYou may or may not know that the number 0 is considered to be even in the world of mathematics, because it is an integer (a whole number).

For a number to be even, it must result in another whole number when divided by two; therefore, the number 10 is even because if you divide it by 2 you get 5 – a whole number; the number 5 is not even though, because when divided by 2 you get 2.5 – not a whole number.

If you divide 0 by 2 you end up with 0 again, and 0 is a whole number, making it pass the test to qualify as an even number.

When it comes to the roulette table though, things don’t seem to work in the same way.

It’s understandable that a 1:1 red or black bet would lose if the ball landed on zero because that pocket is green; but a 1:1 bet on even would lose if the ball landed on zero, yet zero is an even number.

So what is going on here?

Why Zero is Not Even in Roulette

House EdgeIn the casino, the rules are different, and the casino gets to decide what goes.

It may not be mathematically correct, but the zero does not count as an even number in roulette because the house uses the zero to create their house edge.

Although it is possible to bet on the zero using a few inside bets, it is excluded from all outside bets, so the house always has a 1 in 37 chance of winning every outside bet on the table.

Without the zero, the house would not be able to maintain their edge of 2.70% (on European roulette).

This edge exists because there is a 2.7% chance of the ball landing on any single number on the wheel. If you divide 100(%) by 2.7 you get 37 – the same number as there are spaces on the wheel.

Combine this with the fact that the casino doesn’t pay put fair odds – for example there is a 1 in 37 chance of any number coming up but a straight up bet only pays 35:1 – and the casino have their built in edge, guaranteeing they will make money in the long run.

Why Does Roulette Use a Zero?

Roulette Table Zero Symbol Replaced

Roulette has been around as we think of it today since the 1790s, and humankind has come a long way since then.

Zero was considered to be neither odd nor even back in the 1700’s, so it was an ideal choice for the ‘house’s number’ in the game of roulette.

The thinking around this has changed over the years though as we have become more advanced, and now zero has been proven to be an even number by the rules of mathematics, but the game of roulette is steeped in history and tradition so nobody has ever bothered to change it.

The point is that it doesn’t really matter what image is on the green space on the board and wheel, what it represents is what matters. Snakes and Ladders is still the same game if the snakes are swapped out for hosepipes, right? Well roulette is still roulette if the zero is replaced by something else.

It can therefore be helpful to think of the zero as an extra pocket with a non-numerical symbol on it rather than a zero. Indeed, if you look at the American wheel there is an additional slot with 00, or double zero, on it.

Double zero is not really a number at all – you can’t have 2 lots of nothing – and in fact, if you do look at 00 as a number it just becomes 0 again and would therefore also have to be even, creating a huge imbalance between odd and even numbers on the wheel. It just doesn’t work.

So when it comes to roulette, just think of any green pocket as ‘something else’; a square, a smiley face, the initials of the casino, anything.


Can I Challenge the Casino About the Zero Being Even?

You can if you want but you won’t get very far.

The casino set the rules of their games in their buildings, so it doesn’t matter that they are technically incorrect. So long as the game rules are available there’s nothing you can do.

You essentially accept their terms and conditions when you sign up or walk through the door.

Do Any Casinos Treat the 0 as an Even number?

No. If they did they wouldn’t make any money on the game.

This might seem unfair but they are providing a service in running the game in the first place, and the house edge they have built in is their fee for that. Should they run roulette tables for free? It would be nice for us if they did but no business operates in this way.

We pay for all other forms of entertainment and gambling/casinos are no different.