Dice Roller

❓ How to Use

Quick start for rolling fair dice and reading results.

• Select a die type (D4, D6, D8, D10, D12, D20, D%) or choose Custom and enter sides.
• Set # of Dice and Anim Duration for visual feedback speed.
• Click Roll or set Auto Rolls to repeat automatically.
• Use Advantage / Disadvantage for two-roll comparisons.

🎲 Rolling Modes

Choose the mode that fits your game mechanics.

• Normal: Roll N dice and sum results. Example: 3×D6 → sum 3–18.
• Advantage: Roll 2 dice, take the higher. Common for D20 checks.
• Disadvantage: Roll 2 dice, take the lower. Symmetric to Advantage.
• D% (Percentile): Uniform integers from 1 to 100.

📈 Probability Basics

Understand distributions for better expectations.

• Uniform faces: A fair D6 has P(1)=…=P(6)=1/6.
• Sum of dice: Tends toward a bell shape (discrete). Middle sums occur more often.
• Advantage/Disadvantage: Skews outcomes higher/lower respectively.
• Law of Large Numbers: As rolls increase, empirical stats → true probabilities.

⌨️ Keyboard Shortcuts

Work faster with keys (desktop).

• Ctrl + Enter — Roll
• Ctrl + A — Advantage
• Ctrl + D — Disadvantage
• Ctrl + L — Reset stats

🧭 Best Practices & Tips

• Shorter animation helps stress‑testing; longer feels more tactile.
• Try multiple dice for more stable sums (e.g., 4×D6 yields fewer extreme values).
• Change Custom Sides for non‑standard dice (D3, D7, D24, etc.).
• Use history to review streaks and extremes; export via copy if needed.

🔐 Fairness & RNG

How randomness is generated.

• Uses crypto.getRandomValues when available for high‑quality randomness.
• Falls back to Math.random() if necessary.
• Each die is independent; bias is minimized.

❔ FAQ

• What is D%? A percentile die from 1–100, uniform.
• Can I save settings? Yes, settings auto‑save to your browser and restore next visit.
• Why do middle sums appear most? More combinations produce middle totals when summing dice.
• Do results leave my device? No—everything runs locally in your browser.

🛡️ Privacy & Accessibility

• All logic runs in your browser; no data is sent to a server.
• Live region announcements assist screen readers after each roll.
• Keyboard shortcuts and visible focus states improve usability.
• Dark mode supported via system preference and .dark-mode class.

⚙️ How Randomness Works in This Tool

Modern browsers provide high‑quality randomness suitable for most educational and gaming contexts.

This dice roller prefers crypto.getRandomValues when available. The Web Crypto API produces uniformly distributed 32‑bit integers using a cryptographically secure pseudorandom number generator (CSPRNG) provided by the browser/OS. We map that uniform integer into the target range using the modulo operation and an offset to obtain a result from 1 to the number of sides. When crypto isn’t available (older environments), we fall back to Math.random(), which is still uniform for most practical purposes, but not cryptographically secure.

Each die result is independent: the probability of any face on a fair D6 is 1/6 on every roll. Independence means the outcome of one roll does not affect the next, and streaks—while they can feel surprising—do not violate fairness. Over many trials, the observed frequencies converge toward the true probabilities by the Law of Large Numbers.

🧮 Understanding Dice Sums and Distributions

Why the middle totals show up more often when summing multiple dice.

Rolling a single fair die (e.g., D6) yields a uniform distribution—each face is equally likely. However, the sum of multiple independent dice is not uniform. With two D6, there is exactly one way to get a sum of 2 (1+1) but multiple ways to get a 7 (1+6, 2+5, 3+4, 4+3, 5+2, 6+1). As the number of dice increases, the distribution of sums becomes more bell‑shaped (a discrete approximation of the normal distribution by the Central Limit Theorem). This is why middle sums are more frequent and extremes are rare.

• Two D6: Sum range 2–12; 7 is most common.
• Three D6: Sum range 3–18; middle values cluster more tightly.
• Many dice: The shape becomes increasingly peaked at the center with thinner tails.

In practice, this has design implications: using more dice produces outcomes that are more predictable around the center, which is useful for systems that want fewer extreme results.

📊 Advantage & Disadvantage: Intuition

Picking the higher of two rolls increases expected results; picking the lower decreases them.

With Advantage, you roll two dice of the same type and take the higher value. This skews the distribution upward—extremely low results become less likely, and high results become more common. Disadvantage does the opposite: low outcomes appear more frequently while high outcomes are suppressed. On a D20, for example, Advantage raises the expected value by a few points compared to a single roll, which can make meeting target thresholds noticeably easier.

You can observe this effect empirically with this tool by performing many Advantage rolls and comparing the per‑face counts to normal rolls. The shift in the distribution becomes apparent as the sample size grows.

🏫 Practical Use Cases

From tabletop gaming to classroom demonstrations and QA testing.

• Tabletop RPGs: Run quick checks, simulate Advantage/Disadvantage, or handle percentile rolls.
• Education: Demonstrate randomness, independence, and convergence with live per‑face statistics.
• Game Design: Explore how changing dice counts affects variance and player experience.
• QA & Testing: Generate reproducible random sequences for UI stress tests and interaction timing.

The combination of history logs and per‑face stats makes it easy to analyze runs, discuss probability concepts, and save screenshots for lab reports or design notes.

🧪 Fairness Checks & Best Practices

Simple experiments you can run to validate behavior.

• Uniformity check: Roll a D6 a few hundred times. Each face should appear roughly 1/6 of the time.
• Independence check: Look for any predictable patterns in successive outcomes—there shouldn’t be any.
• Parameter sweep: Compare results across animation durations and auto‑roll counts to confirm no bias.
• Edge cases: Try custom dice with unusual side counts (e.g., D3, D7) to verify correct range handling.

While true statistical testing requires larger samples and formal methods (e.g., chi‑square tests), these quick checks are sufficient to build confidence in everyday use.

💡 Tips for Effective Use

• Short animations are ideal for large sample experiments; longer animations provide tactile feedback for live play.
• Use multiple dice when you want more predictable sums; use single dice to maximize variance.
• Leverage the history table to spot streaks and extremes; reset stats between experiments for clarity.
• Store your preferred configuration in the controls—settings are automatically restored on your next visit.