Dice: Over/Under Rules and Provably Fair Rolls

What Is Crypto Dice?

Crypto dice is the original crypto gambling game — the format that launched an entire industry. The mechanic is beautifully simple: a random number between 0 and 99.99 is generated, and you bet on whether the result will land over or under a target number that you choose.

That's the whole game. And yet, dice is one of the most mathematically elegant and player-friendly formats ever created. With RTPs commonly hitting 99% (a house edge of just 1%), crypto dice gives players the best expected return of practically any casino game.

Play it yourself on Wild.io: Dice Originals (provably fair in-house version) or Dice by Spribe.

How Does Over/Under Work?

Every dice round follows this flow:

1. Set your bet amount. Choose your crypto wager.
2. Pick a target number. Use the slider to select any value between 0 and 99.99.
3. Choose over or under — bet that the result will be above or below your target.
4. Roll. The game generates a provably fair random number.
5. Win or lose. If the result falls on your predicted side of the target, you win.

The Slider: Your Risk/Reward Control

The slider is the heart of the dice interface. Moving it changes three things simultaneously:

The relationship is simple: Payout = (100 / win probability) × (1 − house edge). At 99% RTP with a 50% win chance, you get 1.98× instead of the mathematically fair 2.00×. That 0.02× gap is the casino's 1% edge.

Why Does Dice Have the Best RTP in Crypto?

Most crypto dice games run at 99% RTP — meaning a house edge of just 1%. Compare that to other formats:

Why is dice RTP so high? Because the game is simple to operate. There are no complex animations, no licensing fees for third-party providers, and minimal server computation. When a casino builds dice in-house (like Wild.io's provably fair version), the savings get passed to players as a lower house edge.

This is why the crypto dice game remains the workhorse of crypto gambling: it's the most efficient game for players who prioritize expected value over entertainment spectacle.

How Did SatoshiDice Launch an Industry?

Crypto dice has a special place in blockchain history. SatoshiDice (accessed August 2026), launched in April 2012 by Erik Voorhees, was one of the first Bitcoin gambling platforms ever created. At its peak, SatoshiDice transactions accounted for over half of all Bitcoin transactions on the network.

The game was revolutionary for two reasons:

1. On-chain betting — bets were placed by sending Bitcoin to specific addresses, each representing a different win probability. Results were determined by transaction hashes.
2. Provable fairness — the use of blockchain data for result generation meant outcomes were verifiable, establishing the concept that would evolve into modern provably fair systems.

PrimeDice, launched in 2013, refined the model with a smoother interface and introduced the slider mechanic that's now standard across crypto dice games. These platforms proved that crypto gambling could be more transparent and player-friendly than traditional online casinos — a philosophy that continues with platforms like Wild.io.

What Does the Math Look Like in Detail?

Win Probability

For a "roll under X" bet:

• Win probability = X / 100
• Example: Roll under 33.33 → 33.33% chance of winning

For a "roll over X" bet:

• Win probability = (99.99 − X) / 100
• Example: Roll over 66.66 → 33.33% chance of winning

Payout Calculation

Payout multiplier = (1 − house edge) / win probability

With 1% house edge: Payout = 0.99 / (X/100) = 99 / X (for roll under)

Expected Value Per Bet

EV = (win probability × payout × bet) − bet EV = bet × (win probability × payout − 1)

At 99% RTP, no matter where you set the slider: EV = bet × (0.99 − 1) = −0.01 × bet

You lose 1 cent per dollar wagered on average, regardless of your target number or bet direction. The house edge is mathematically constant.

How Do You Verify a Dice Roll Is Fair?

Dice is the ideal game for provably fair verification because of its simplicity. One roll, one number, one result. Here's the verification flow:

1. Before the roll, the server generates a random seed and commits its SHA-256 hash to you.
2. You provide (or accept a default) client seed and nonce.
3. The result is computed by combining server seed + client seed + nonce through HMAC-SHA512 (accessed August 2026), then converting the hash output to a number between 0 and 99.99.
4. After the round, you can reveal the server seed and verify the hash matches the pre-commitment, and that the derived number matches your game result.

Because the server seed is committed before your roll, the casino can't manipulate the outcome after seeing your bet. And because your client seed is included, the casino can't pre-compute a losing result without knowing your contribution.

For the full verification walkthrough, visit our provably fair casino trust course or read the verification guide.

What Strategy Should You Use for Dice?

Bankroll Management

Dice's high RTP means your bankroll erodes slowly, about 1% per wager. This makes it suitable for high-volume play, but the math still works against you over time. Use the dice game as an opportunity to practice strict bankroll discipline:

• Set a session bankroll and stick to it
• Choose bet sizes of 1–3% of that bankroll
• Track your results. The provably fair data makes auditing easy

Low vs. High Target Numbers

Betting on high-probability outcomes (roll under 90) gives you frequent small wins. Betting on low-probability outcomes (roll under 5) gives rare large wins. Your expected loss per bet is identical either way. Choose based on the session experience you prefer, not because you think one side has better odds.

Progression Systems Don't Work

Martingale and other bet-doubling systems are especially popular in dice because of the fast round times. They don't overcome the house edge. What they do is concentrate your risk into rare but devastating losing streaks. A 99% win-rate bet loses 10 times in a row with probability (0.01)^10 — that's one in 10 quadrillion, astronomically unlikely. But a 50% bet loses 10 times in a row about once every 1,024 sequences, which is very possible in a long session.

The Bottom Line

Crypto dice is the game that started it all — from SatoshiDice's blockchain bets in 2012 to today's polished provably fair implementations. It offers the highest RTP in crypto gambling, the most transparent risk/reward mechanics, and the cleanest provably fair verification of any game format.

The slider puts complete control in your hands. You see your exact win probability and exact payout before every roll. No game is more honest about its mathematics. Whether you play at Dice Originals or explore the Dice by Spribe variant, you're playing the purest form of crypto gambling that exists.

Just remember: 99% RTP is excellent, but it's still less than 100%. Manage your session with the provably fair course knowledge and responsible habits in mind.