Coin Flip & Dice Roller

What This Actually Does

Here's what you're getting: a coin that flips heads or tails, and dice that go from d4 up to d100. You can flip one coin at a time or roll up to 10 dice together - works great for rolling character stats or calculating damage in one shot. Everything runs on cryptographically secure randomness (basically the same tech that keeps your passwords safe), so it's legit random, not some weird pattern you can game.

Results pop up instantly - no loading, no spinning animations that waste your time. The interface is colorblind-friendly because everyone should be able to see their nat 20. Works on your phone, tablet, laptop, whatever. You can check your last 10 rolls in the history if you need to verify something or just want to see how your luck's been running.

The random generators available are: coin flip (heads/tails), d4 (1-4), d6 (1-6), d8 (1-8), d10 (1-10), d12 (1-12), d20 (1-20), d100 (1-100), plus custom ranges when you're rolling multiple dice. Pick your dice type, pick how many, hit roll. That's it.

When You'll Actually Use This

D&D Player's Quick Reference

Dice notation looks weird at first but it's straightforward once you get it. When you see "2d6+3" that means roll two six-sided dice and add 3 to the total. The first number is how many dice, the "d" stands for dice, the second number is how many sides, and anything after the plus sign gets added to your roll. So 1d20+5 means one twenty-sided die plus five.

Common roll types you'll make constantly: attack rolls (1d20 + your attack bonus to see if you hit), skill checks (1d20 + whatever modifier applies), saving throws (1d20 + the relevant save bonus when something bad happens), damage rolls (depends on your weapon - maybe 1d8+4 for a longsword), and initiative (1d20 + dex modifier to see turn order in combat).

Advantage and disadvantage are huge in 5e. With advantage, roll 2d20 and take the higher number - your odds of hitting that 15+ jump from 30% to about 51%. Disadvantage is the opposite: roll 2d20, take the lower one. Getting advantage on your attacks or forcing disadvantage on enemies is one of the best tactical moves you can make.

For rolling character stats, the standard method is 4d6 drop lowest, repeated six times (once for each ability score). Roll four dice, ignore whichever one's lowest, add up the other three. You'll usually end up with scores between 8 and 16, with the occasional 17 or 18 if you're lucky. Some DMs let you reroll if your total modifiers are too low.

Critical hits happen on a natural 20 (the die shows 20, not including modifiers) - you automatically hit and roll damage dice twice. Critical fails on a natural 1 mean you automatically miss, though some DMs add extra consequences. That's why everyone at the table celebrates nat 20s and groans at nat 1s. Quick probability fact: on a straight d20 roll, every number has exactly a 5% chance of showing up.

If you're playing on virtual tabletops like Roll20 or Foundry VTT, you can still use this for quick rolls when you don't want to open the character sheet. It's also handy if you're planning characters between sessions or need to test some probability math for your build.

Digital vs Physical Dice

Everyone asks this: "Is it really random?" Short answer - yes, for gaming purposes. This uses JavaScript's Math.random() function which is pseudorandom. That means it's generated by an algorithm, not true quantum randomness, but the pattern is so complex and unpredictable that you can't game it. Totally fine for D&D, board games, making decisions. Not fine for cryptography or securing nuclear launch codes, but you probably weren't planning to do that anyway.

Here's the thing people don't realize: physical dice aren't perfectly random either. Manufacturing imperfections mean some sides are slightly heavier. The way you shake and throw them affects results. That tiny chip on your favorite d20 might be skewing it toward 17s. Casinos replace their dice constantly because even small wear patterns affect probability. Your lucky dice? Probably just confirmation bias.

For casual gaming, digital randomization works great. For serious gambling or scientific research, you'd want hardware random number generators that measure quantum events. But we're talking about deciding if your barbarian hits the orc, not running Monte Carlo simulations for particle physics.

The ritual aspect of rolling physical dice is real though. Some players love the tactile feel of chucking dice across the table. There's definitely something satisfying about the clatter of dice in a dice tower or the way a d20 spins before landing on that crucial attack roll. That's totally valid - half the fun of tabletop gaming is the physical experience.

Plus digital dice can't roll off the table, which happens at least three times per session in my experience. They can't get lost, don't take up space in your bag, and you're never stuck with that cheap d20 from a board game because your nice set is at home. Think of this as a backup that's always available, not a replacement for your collection of shiny math rocks.

Probability Quick Reference

A single d20 has flat probability - every number from 1 to 20 has exactly a 5% chance of coming up. Roll it 100 times and you should get each number about 5 times (though randomness means it won't be exact). This is why d20s feel so swingy - you're just as likely to roll a 2 as an 18.

Now roll 2d6 instead and things get interesting. You can't roll a 1 (minimum is 2), can't roll higher than 12, and 7 is way more likely than anything else. There's a 16.67% chance of rolling exactly 7 because there are six ways to make it (1+6, 2+5, 3+4, 4+3, 5+2, 6+1). Meanwhile there's only one way to roll a 2 (1+1) or a 12 (6+6), so each has about 2.78% probability.

With 3d6 the curve gets even steeper. Results cluster around 10-11, and extreme rolls become rare. This is why some games use multiple dice for stats or damage - it creates more consistent, predictable results instead of wild swings. A weapon that does 3d6 damage is more reliable than one that does 1d18, even though the ranges are similar.

Advantage in D&D changes your odds dramatically. On a flat d20 roll, you've got a 50% chance of hitting 11 or higher. With advantage (rolling 2d20 and taking the higher), that jumps to 75%. The boost is even bigger for high target numbers - your chance of hitting 18+ goes from 15% to about 27.75%. It's roughly equivalent to a +5 bonus, which is massive.

Critical hits on a d20 happen 5% of the time normally. With advantage, you've got roughly a 9.75% chance because you get two chances to hit that 20. Quick way to calculate it: the probability of not getting a 20 is 95% (19/20). Rolling twice means (19/20) × (19/20) = 0.9025, so there's a 9.75% chance you'll get at least one 20.

Here's a practical example: you need to roll 15 or higher on a d20. That's 6 numbers out of 20, so 30% normally. With advantage, the chance of rolling under 15 twice is (14/20) × (14/20) = 0.49, meaning you've got a 51% chance of success. You just went from failing more often than not to succeeding more often than not. This is why tactics that give you advantage are worth using even if they cost you a turn.

Gaming Resources

If you're getting into tabletop gaming or want to understand dice probability better, here are some solid resources. D&D Beyond's dice roller includes modifiers and has character sheet integration. Wizards of the Coast's official site has the basic rules for free if you're new to D&D. AnyDice is incredible for calculating complex probability - plug in "output 2d6" and it shows you the exact distribution. Board Game Geek has guides on dice mechanics in different games. Roll20 is free for basic virtual tabletop play if your group's remote.

Frequently Asked Questions

Tyler here - built this during a D&D session when we couldn't find dice. Also great for settling roommate disputes about chores.

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