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Roulette jackpot maths: contribution, return and the pool that would break even
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A jackpot on a roulette table is a side bet with a progressive prize. Like all side bets it has its own house edge, separate from the wheel's, and like most side bets that edge is large. The arithmetic is simple once the pieces are separated, and separating them is the point of this page.
Three pieces
- The roulette bet. Standard payouts on a standard wheel: 2.70% edge on single zero.
- The contribution. A percentage of each qualifying bet taken for the pool: 1% on Dragon Jackpot, 0.99% on Age of the Gods.
- The jackpot return. What flows back to players from the pool, averaged over everyone who contributed.
Your total return is the roulette return on the money that reached the wheel, plus your share of the jackpot return.
Effective edge with the contribution
A £1 bet with a 1% contribution: 99p plays roulette and returns 99p × 97.30% = 96.33p on average. The 1p goes to the pool. Before any jackpot return, your expected return is 96.33% and the effective edge is 3.67%. For a single spin that is the difference between a £13.50 expected loss and an £18.35 one over 100 spins at £5.
Put it into practice
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Why the jackpot return is less than the contribution
The pool is funded entirely by contributions. If every penny contributed came back as prizes, the long-run jackpot return would equal the contribution and the side bet would be free. In practice part of the contribution funds the seed of the next pool after a win, part covers the operator's and provider's share, and the rest is paid out. So the jackpot return averaged across all players is some fraction of the 1%, and the gap is the side bet's house edge. Providers do not publish the fraction.
The break-even pool
For a player, a jackpot bet has positive expectation only when the current pool is large enough that (chance of winning per spin × pool) exceeds the contribution per spin. The chance of winning per spin is not published and is stake-weighted. Without it the break-even pool cannot be calculated, which is why no responsible figure exists for "play when the pot is above £X". The honest statement is that for almost any realistic pool, the contribution is a cost with a very small chance of a very large rebate.
The 38th pocket
Age of the Gods' RNG tables fund their bonus partly through an extra pocket. A 38th pocket costs you the same as a 00: the straight-up still pays 35:1 but wins 1 in 38, and every bet's return drops from 97.30% to 94.74%. That is a 2.56-point cut on every spin, applied whether or not you care about the jackpot, and it is on top of the 0.99% contribution. The bonus pocket pays something when hit, which claws a little back, but the structure is: an American-wheel price for a European-wheel game, plus a side bet.
In pounds, 100 spins at £5
| Table | Expected cost |
|---|---|
| Plain European wheel | £13.50 |
| Dragon Jackpot, toggle off | £13.50 |
| Dragon Jackpot, toggle on | about £18.35 before any jackpot return |
| Age of the Gods RNG | about £26 before jackpot return |
The conclusion the numbers point to
An opt-in jackpot at 1% is an entertainment surcharge of about a fifth on top of the price of roulette. A built-in jackpot with an extra pocket roughly doubles the price. Neither is a scandal; both are side bets, and side bets are always the expensive part of the table. Decide whether the pool on screen is worth that to you, and if it is not, the plain wheel is right there.
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Good to know
Does a jackpot contribution come out of my bet or on top of it?
Out of it. On a £1 bet with a 1% contribution, 1p funds the pool and 99p plays the roulette bet. Your roulette return is on the 99p; the 1p is gone unless you are the one who wins the pool.
Can a progressive jackpot ever be worth playing for?
Only when the pool is large enough that the expected jackpot return per spin exceeds the contribution. That requires knowing the trigger odds, which providers do not publish, so in practice the point cannot be found and the bet is a cost.