Education only. This is a free educational reference about gambling math and risk. We never take a wager, hold a stake, or run a book — there is no deposit, no cash-out, and no bet to place here. Publishing odds and education is legal speech; taking bets is a licensed activity and is out of scope. Nothing here is betting, investment, legal, or financial advice.

Gambling calculators

Every calculator runs entirely in your browser — nothing is sent anywhere, no bet is placed. The math mirrors our §4.7 odds engine (integrations/soapbox/gambling.mjs).

1 · Expected value (EV)

Your honest win probability vs the price offered. Positive EV is rare; the vig usually makes it negative.

Your win probability (%)

Decimal odds offered

Stake ($)

2 · House edge per game

Pick a game to see its house edge, RTP, and your expected loss over a session.

Game / bet

Bet size ($)

Number of bets

3 · Odds converter

American ↔ decimal ↔ fractional ↔ implied probability. Enter ONE field, convert.

American (e.g. -110 or +150)

Decimal (e.g. 1.91)

Fractional (e.g. 7/2)

Implied prob (%)

4 · Parlay / accumulator

Combine legs (decimal odds, comma-separated). Every leg must win — the payout grows, but so does the combined vig you pay.

Legs (decimal odds)

Stake ($)

5 · Bankroll & Kelly fraction

The Kelly criterion sizes a bet to your edge. If you have no edge (the normal case), Kelly says bet nothing. Most who use it bet a fraction of full Kelly to cut variance.

Bankroll ($)

Your win probability (%)

Decimal odds

Kelly fraction

6 · Lottery expected value

Ticket cost vs jackpot × probability. It is almost always deeply negative — and this ignores taxes and jackpot-sharing, which make it worse.

Ticket cost ($)

Jackpot ($)

Jackpot odds: 1 in …

Prefill from a real game on the lottery page.