Randomizers & Probability
Coin flips, dice, spinner wheels, random generators, and live probability simulators — plus statistics calculators, all running in your browser.
21 tools
Binomial Distribution Calculator
Free binomial distribution calculator. Enter n, p, and k for the exact P(X=k), P(X<=k), P(X>=k), mean and variance, plus a bar chart of the distribution.
Central Limit Theorem
See the central limit theorem in action: roll 2d6 thousands of times and watch the sums build a bell curve, with the dice intuition explained.
Coin Flip
Flip a coin online for free. Get a fair, random heads or tails instantly, flip many at once, and keep a running tally. Great for quick, unbiased decisions.
Coin Flip Simulator
Simulate thousands of coin flips and watch the heads proportion converge to 50% in real time. A live law-of-large-numbers demo for stats class.
D20 Roller
Free d20 roller for D&D and tabletop RPGs. Roll a single 20-sided die instantly for attacks, saves, and ability checks, with full roll history.
Dice Roller
Free online dice roller. Roll any dice with NdM notation (2d6, 1d20, 3d6+2), quick d4-d100 buttons, individual rolls, totals, and roll history.
Dice Simulator
Free dice probability simulator. Roll 2d6 thousands of times and watch the sum distribution converge to the bell curve - see why 7 is most common.
DnD Dice Roller
Free D&D dice roller with the full polyhedral set (d4-d100) and d20 checks rolled with advantage or disadvantage. Roll history included.
Expected Value Calculator
Free expected value calculator. Add each outcome value and its probability to get E[X] = sum of value times probability, with a per-term table.
Law of Large Numbers
See the law of large numbers in action: flip a coin thousands of times and watch the proportion of heads converge to 0.5 (and why a streak isn't "due").
Magic 8 Ball
Ask the online Magic 8 Ball a yes-or-no question and get one of the 20 classic answers. Free, instant, no app — shake the ball for fortune-telling fun.
Normal Distribution Calculator
Free normal distribution calculator. Enter mean, standard deviation and x for the z-score, pdf, and probabilities P(X<=x), P(X>=x), and P(x1<=X<=x2).
Random Letter Generator
Free random letter generator. Pick one or many random letters A to Z, choose upper or lowercase, or vowels only — perfect for word games and teaching.
Random Name Picker
Free random name picker. Paste a list, spin, and select one random name fairly for classrooms, giveaways, and prize draws. No sign-up needed.
Random Number Between 1 and 100
Pick a random number between 1 and 100 instantly. Great for games, giveaways, decisions, and classroom picks — tap once for a fair 1 to 100 result.
Random Number Generator
Free random number generator: set a range, generate many at once, no-repeat draws, decimals, negatives, Gaussian, plus binary, octal, and hex output.
Random Team Generator
Free random team generator. Paste names, choose how many teams, and split everyone into fair, evenly-sized teams instantly. No sign-up needed.
Spinner Wheel / Random Picker
Free online spinner wheel. Add your own entries, spin a colorful wheel, and let chance pick a fair random winner. Works on any device, no sign-up.
Standard Deviation Calculator
Free standard deviation calculator. Paste numbers for the mean, variance, and both population (n) and sample (n-1) standard deviation, with worked steps.
Wheel of Names
Spin a free wheel of names to draw a random winner for classroom picks, raffles, and giveaways. Add names, spin, and remove winners as you go.
Yes or No Wheel
Can't decide? Spin the free yes or no wheel for an instant answer. Optional Maybe slice for tougher calls. Fast, fair, and works on any device.