About Flip a Coin
This coin flip is a fair heads or tails decision maker. Each flip uses one unbiased random bit from your browser, so heads and tails are exactly equally likely. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
The tally under the coin counts heads and tails since you opened the page or pressed Reset. After a few flips the shares wander, and they only settle near 50% after hundreds of flips. A run of five heads in a row is normal and does not mean the next flip is due to be tails.
If you have reduced motion switched on in your device settings, the coin skips the spin and shows the result at once.
How to use Flip a Coin
- Choose what to generate: numbers, a coin flip, dice, a shuffled list, a name picker or lottery numbers.
- For numbers, enter the minimum and the maximum, then how many numbers you want. Both ends are included.
- Switch on No repeats if every number must be different, and Sort if you want them in order. Pick a number of decimal places for decimals.
- Press Generate (or Flip, Roll, Shuffle or Pick). Each press makes a new independent draw.
- Copy the result or download it as a text file. The coin keeps a running tally of heads and tails until you reset it.
Features
- Unbiased integers: crypto.getRandomValues with rejection sampling, so every value in the range is equally likely.
- Any range up to about 9 quadrillion, whole numbers or up to six decimal places, unique or with repeats, optionally sorted.
- Up to 10,000 numbers in one draw, copied or downloaded as plain text.
- Coin flip with a running tally and a short animation that is turned off when your device asks for reduced motion.
- Dice roller for 1 to 10 dice of 4, 6, 8, 10, 12, 20 or 100 sides, with each die and the total.
- List randomizer and name picker that use a Fisher-Yates shuffle with unbiased index draws.
- Lottery numbers for common formats or your own: different main numbers, optional bonus numbers from a separate pool.
- Works on a phone, with large touch targets and no sign-up.
Worked examples
Ten flips gives Often 4 to 6 heads
Seven heads out of ten happens about 12% of the time with a fair coin.
Five heads in a row gives Chance 1 in 32
The next flip is still 50% heads, because flips are independent.
Good to know
About the randomness
Draws come from crypto.getRandomValues in your browser with rejection sampling, so every outcome is equally likely. It is strong randomness for everyday use but not a certified lottery or gaming source.
Privacy: how it works
- Everything is generated by code running in your browser tab. Your ranges, lists and names are not sent to Ulkaa or to any other server.
Tips
- For a raffle, number the entries from 1 to the count and ask for one number with the range set to match.
- To pick several winners from a list, use the name picker. It never picks the same name twice in one draw.
- Decimals are generated as a whole number of the last decimal place and then scaled, so they are evenly spread too.
- For a simulation of many dice, ask for numbers from 1 to 6 with repeats allowed rather than rolling by hand.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Your ranges and lists are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Your ranges and lists are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
Is the coin flip fair?
Yes. Each flip is a single unbiased random bit, so heads and tails are equally likely every time.
Does a streak make the other side more likely?
No. Each flip is independent, so past results do not change the next one. That belief is called the gambler's fallacy.
More Random Number Generator pages
- Random Number GeneratorSet a range, press Generate and get fair random numbers, or flip a coin, roll dice, shuffle a list or pick a name.
- Dice RollerChoose how many dice and which kind, then roll to see every die and the total.
- List RandomizerPaste your items, one per line or separated by commas, and shuffle them into a random order.
- Random Name PickerPaste a list of names and pick one winner, or several different winners, at random.
- Lottery Number GeneratorChoose a format such as 6 from 49 and get a quick pick, with different numbers in order.
- Random Number 1 to 10Press Generate for a random whole number from 1 to 10, both included.
- Random Number 1 to 100Press Generate for a random whole number from 1 to 100, both included.
- Random Decimal GeneratorGet random decimals between 0 and 1, or set your own range and number of decimal places.