Free Gambling and Betting Maths Tools
Seventeen calculators and verifiers that run entirely in your browser. Nothing is sent anywhere, nothing needs an account, and every one shows its working rather than returning an answer you have to trust.
The Tools
Wagering requirement calculator
Prices what clearing a bonus costs in house edge, and tells you when that exceeds the bonus itself.
Crash round verifier
Recomputes a crash round from its seeds and shows the HMAC digest, the integer and the multiplier.
Coin flip verifier
Recomputes a flip and shows the byte that decided it.
Dice calculator and verifier
Multiplier, expected value and win frequency for any target and house edge, plus a seed verifier for a roll.
Mines calculator and verifier
Full payout table with survival odds for any mine count, plus a seed verifier that shows where the mines were.
Plinko calculator and verifier
Exact bucket probabilities for any row count, the RTP your paytable produces, and a seed verifier for a drop.
Hold and no-vig calculator
Two prices in, the sportsbook's cut out, plus the fair line underneath with the margin stripped.
Parlay margin calculator
True odds against offered odds across up to six legs, and the hold that compounds between them.
Odds converter
American, decimal, fractional and implied probability, with the break-even win rate.
Kelly stake calculator
The share of a bankroll an edge justifies, at full, half and quarter Kelly.
Arbitrage calculator
Two books, opposite sides, the stake split that locks a return when the prices sum under 100%.
Limbo calculator and verifier
Win chance and expected value for any target multiplier, plus a seed verifier for a round.
Martingale calculator
How many losses in a row your bankroll covers when you double after a loss, and the exact chance a run busts.
Bankroll calculator
Expected loss, typical swing and the exact chance of profit or ruin for a session at any stake size.
House edge and RTP calculator
Expected loss for any RTP, stake and time played, and what clearing a bonus costs in expected loss.
Bet builder
Parlay and accumulator odds from American, decimal or fractional prices, plus a straight or reverse forecast estimate.
Rakeback and cashback calculator
What a rakeback or cashback rate is worth as a change in the effective house edge, with the cap applied.
Why These Work Differently
A casino’s own verifier could be built to return fair every time, so a tool that only gives a verdict proves nothing. Ours print the intermediate values, and those are identical at every casino regardless of how the final conversion differs.
The calculators follow the same principle. Each one states the formula it uses, so the output can be checked by hand rather than taken on faith. Where a figure varies by provider, the tool asks for your value instead of assuming one.
| Tool | What makes it different |
|---|---|
| Wagering requirement calculator | Handles four stacking multipliers. Most calculators handle the headline figure and the base. |
| Crash round verifier | Shows every intermediate value rather than returning a verdict, so you can compare against any casino's formula. |
| Coin flip verifier | The parity step is simple enough to repeat by hand, which makes it the clearest place to learn the scheme. |
| Dice calculator and verifier | Shows that expected loss per amount staked is identical at every win chance. |
| Mines calculator and verifier | Multipliers are derived from the odds rather than read off a casino's chart. |
| Plinko calculator and verifier | Takes your paytable rather than assuming one, since multipliers vary by provider. |
| Hold and no-vig calculator | Reports hold and overround separately, because pages quoting one as the other are out by a fifth. |
| Parlay margin calculator | Four legs at standard prices hold about 17%. No sportsbook states that and few affiliates compute it. |
| Odds converter | Shows implied probability and break-even rate as the same number, because they are. |
| Kelly stake calculator | States that it trusts your probability completely, which is the part that decides whether it helps. |
| Arbitrage calculator | Says plainly that limits and stale prices are what end this, rather than selling it as a system. |
| Limbo calculator and verifier | Makes the flat expected value across targets visible in one table. |
| Martingale calculator | Prints the expected result per cycle and shows it equals minus the house edge times the amount staked. |
| Bankroll calculator | Uses the binomial distribution rather than a simulation, so the same inputs always return the same chances. |
| House edge and RTP calculator | Shows the break-even RTP for a wagering requirement, which is 97.5% at 40x. |
| Bet builder | Accepts every odds format and prints the break-even chance, which is one divided by the combined price. |
| Rakeback and cashback calculator | Shows that uncapped cashback pays more than rakeback at the same rate, and what the cap takes back. |
Nothing Leaves Your Browser
Every calculation runs client side. Seeds you paste into a verifier are never transmitted, logged or stored, which matters because a server-side verifier would be handling values tied to a real account.
You can confirm this by opening your browser’s network tab while using any of them. No request is made when you press the button.
Using These on Your Own Site
These are free to reference, quote and screenshot. If a tool is useful to your readers, link to it rather than copying the output, because the figures update as the underlying data does.
Our measured payout data is published under CC BY 4.0, so you can reuse the figures with credit and a link back. Full terms are on the payout benchmarks page.
If you find an error in one of the formulas, that is worth telling us about. We will correct it and date the correction. Our editorial standards cover how.
18+ only. Every game these tools cover carries a negative expected value by design, which several of them will show you directly. Free, confidential support is available at GambleAware.