Random Letter Generator

How to use the random letter generator

The generator draws letters the way you would pull tiles out of a bag, except the bag is your browser’s cryptographic random number generator. Everything happens on this page, and the options at the top apply to every tab.

1. Choose the letters to draw from: the alphabet, uppercase or lowercase, all letters, vowels or consonants, and any letters to leave out.
2. On the Letters tab, set how many letters you want, whether repeats are allowed, and equal chances or English letter frequencies.
3. Press Generate, or Ctrl + Enter. One to twelve letters appear as big tiles; longer results appear as text with the separator you picked.
4. Copy the result or download it as a text file. Every draw is also listed in the history, which you can copy or save as a CSV file.

Use the Wheel tab to spin a letter wheel, the Big display tab to show one huge letter at a time to a class (press Space for the next one), the Letter + number tab for combinations such as B7 or for 75-ball bingo calls, and the Fairness test tab to check the generator with a few hundred thousand draws.

Alphabets, vowels, consonants and custom sets

The random alphabet generator knows five alphabets. Each letter list comes from the authority for that language, and every letter is stored with its own capital and small form, so a German ß becomes the capital ẞ, not “SS”.

Choose Vowels or Consonants to make a random vowel generator or a consonant picker; in English that is 5 vowels and 21 consonants, or 6 and 20 with Y as a vowel. Both puts every capital and small letter in the pool, 52 for English. Add digits 0–9 mixes in the ten digits, and Leave out drops any letters you type, so QXZ removes the awkward ones for a word game. The Custom set takes your own characters (ABCDE), or items separated by spaces or commas, such as ch, sh, th and wh for a phonics lesson. A custom set can hold up to 200 items.

The pool preview under the options always shows exactly what can be drawn, and a note explains any option that does not apply, for example English letter frequencies with the Greek alphabet.

How the letters are picked: Web Crypto and modulo bias

Every draw starts with crypto.getRandomValues(), the random number source of the Web Cryptography API that browsers also use for keys and passwords. It fills an array with unpredictable 32-bit numbers, up to 65,536 bytes per call, which the generator respects by asking in chunks.

Turning a random number into one of 26 letters looks easy: take the number modulo 26. But that small step is where many generators go wrong. Take one random byte, with 256 possible values. Since 256 = 9 × 26 + 22, the remainders 0 to 21 each turn up 10 times among the 256 values and the remainders 22 to 25 only 9 times. With a bare byte % 26, A to V each have a 10/256 = 3.906% chance and W, X, Y and Z only 9/256 = 3.516%: A would be about 11% more likely than Z. This is called modulo bias.

The fix is rejection sampling, the “simple discard method” in NIST Special Publication 800-90A: throw away the few values that would make the split uneven and draw again. With 32-bit numbers the generator keeps values below 4,294,967,274, the largest multiple of 26 below 2³², and discards the 22 values above it, about 1 in 195 million. Every letter then has exactly the same number of ways to come up, so there is no bias at all, not just a small one. The same method, scaled to the size of the pool, is used for vowels, custom sets, the wheel, the bingo caller and the numbers in letter + number combinations.

Cryptographic randomness also means the letters cannot be predicted from earlier ones, which matters little for a spelling game but a lot if you use random letters in codes or tickets.

No repeats: draw until every letter is used

With repeats allowed, every letter is drawn independently, so the same letter can come up twice in a row. That happens more often than people expect. The chance that k letters drawn from 26 contain at least one repeat is 1 − (26 × 25 × … × (26 − k + 1)) ÷ 26^k, the same reasoning as the birthday problem:

Choose No repeats on the Letters tab and each letter appears at most once in a batch, like dealing cards from a shuffled deck; you can draw up to the whole pool, which gives the alphabet in a random order. The Big display goes one step further: with No repeats until every letter is drawn it remembers what it has drawn across clicks and only starts a new round once all 26 letters have come up, so no letter is left out of a lesson. The order is as random as a Fisher–Yates shuffle, where every one of the 26! possible orders is equally likely.

English letter frequency

Letters are not equally common in English text. The table below is one well-known count for running English text, from Robert Lewand’s Cryptological Mathematics (2000). Choose English frequency under Chances and the generator draws each letter in proportion to it, so E comes up about 170 times as often as Z. That is useful for word games that should feel like real words, for cipher practice, and for testing text tools. With equal chances, every letter has a 1 in 26 chance, 3.846%.

The order E T A O I N S H R D L U is often quoted from typesetting, but in this table C comes before U. The five vowels A, E, I, O and U make up 38.100% of letters, and J, X, Q and Z are each under 0.2%, which is why the Leave out field has a Skip J Q X Z button. The published figures add up to 99.999% because each is rounded, so the generator uses them as exact whole-number weights: E is drawn 12,702 times in 99,999. Other counts, from dictionaries or other kinds of text, give slightly different numbers and orders.

Spin the letter wheel

The random letter wheel draws one segment for each letter in the pool, up to 100. When you press Spin, the generator first picks the winning letter with the same unbiased method, then turns the wheel to stop on it, so the animation never decides anything and every segment has the same chance. Switch on Remove each picked letter to take letters off the wheel as they are drawn, and Put all back to start again.

The spin lasts under four seconds and only runs when you press the button. If your device asks for reduced motion, or you turn on Reduce motion, the wheel turns straight to the result without spinning, as the Web Content Accessibility Guidelines recommend for animation started by an interaction.

The big display for classrooms and letter games

The Big display tab is a letter picker made for a projector or an interactive whiteboard. It shows one letter as large as the screen allows, and the keyboard runs it so you never have to aim for a button:

• Space, Enter or N draws the next letter, and the last 12 letters stay visible under it.
• F switches full screen on and off.
• T pauses or resumes the timer, which can run for 30 seconds to 3 minutes with each new letter and beep softly when time is up.

Switch on Show categories for a classic categories word game: each new letter comes with 3 to 12 categories, such as Animals, Foods or Things in a classroom, and players race the timer to write one word per category that starts with the letter. A word nobody else thought of scores a point. The category list is our own general one, suitable for school.

Other ideas for random letter games with kids:

• Letter hunt: draw a letter and find three things in the room that start with it.
• Sound it out: younger readers say the sound of the letter, then a word that begins with it. Use lowercase, or a custom set of digraphs such as sh, ch and th.
• Alphabet order: draw five letters with no repeats and put them in alphabetical order.
• Word builder: draw seven letters with English frequency and make the longest word you can.
• Handwriting warm-up: draw ten letters, uppercase and lowercase, and write each one.

Letter + number combinations and bingo calls

The Letter + number tab pairs a random letter from your pool with a random whole number, for seat and table numbers, grid references, code names such as K7 or practice license plates. Pick the range (0 to 9,999), the format (A7, A-7 or A 7) and whether to zero-pad, so 1 to 10 gives A01 to A10. With the 26 English capitals and the numbers 1 to 9 there are 26 × 9 = 234 possible combinations; with 0 to 99 there are 26 × 100 = 2,600.

Bingo calls 1–75 turns the tab into a caller for 75-ball bingo at home or in class. Each number is called once in a random order, with the letter of its column: B 1 to 15, I 16 to 30, N 31 to 45, G 46 to 60 and O 61 to 75, the layout written into state bingo rules. A 5 × 15 board marks every number called, and Copy calls lists them for checking a card.

Check it yourself: the fairness test

A random letter generator is easy to call fair and hard to check by eye. The Fairness test tab draws 10,000, 100,000 or 1,000,000 letters with your current options, counts each letter and compares the counts with what the chances say to expect, using the chi-square goodness-of-fit test from the NIST/SEMATECH e-Handbook of Statistical Methods:

χ² = Σ (observed − expected)² ÷ expected
degrees of freedom = number of letters − 1

For the 26 English letters there are 25 degrees of freedom, and a χ² above 37.652 would happen only 5% of the time with a fair source. The tab reports χ², the degrees of freedom and the p-value, the chance of counts at least this uneven from a fair generator. Expect a p-value below 0.05 in about one run in twenty even when everything is working: that is what 5% means. A generator with modulo bias, or one that favors a letter, fails run after run once the number of draws is large enough.

Random letters in a spreadsheet or in code

In a spreadsheet, =CHAR(RANDBETWEEN(65,90)) gives a random capital letter, because the character codes 65 to 90 are A to Z; use 97 to 122 for lowercase. The result changes every time the sheet recalculates. In JavaScript, the method this page uses looks like this:

const letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
const limit = 2 ** 32 - (2 ** 32 % 26) // 4,294,967,274
const word = new Uint32Array(1)
do crypto.getRandomValues(word)
while (word[0] >= limit) // discard the 22 values that cause bias
console.log(letters[word[0] % 26])

Private by design

• Nothing is uploaded. Every letter is drawn in your browser, and the page’s security policy allows connections only back to this site. The generator makes none.
• Draws are not stored. The history lasts for this visit only and is gone when you reload. Your settings, including a custom set, are kept in your browser’s local storage under one key.
• No account and no cookies. Once the page has loaded, it works offline.

Sources

• W3C, Web Cryptography API: getRandomValues and its 65,536-byte limit.
• NIST SP 800-90A Rev. 1 (2015), Recommendation for Random Number Generation Using Deterministic Random Bit Generators, Appendix A.5: converting random bits into a random number without bias.
• NIST Dictionary of Algorithms and Data Structures: Fisher-Yates shuffle.
• NIST/SEMATECH e-Handbook of Statistical Methods, §1.3.5.15 Chi-Square Goodness-of-Fit Test and §1.3.6.7.4 Critical Values of the Chi-Square Distribution.
• Lewand R E (2000). Cryptological Mathematics. Mathematical Association of America, pp. 36–37, Table 1, as reproduced by the Hong Kong University of Science and Technology and Emory University.
• Real Academia Española: Exclusión de «ch» y «ll» del abecedario.
• Rat für deutsche Rechtschreibung (2024). Amtliches Regelwerk, Vorbemerkungen and § 25.
• Rydberg-Cox J, A Digital Tutorial for Ancient Greek based on White’s First Greek Book: the Greek alphabet.
• Harvard University, Beginner’s Russian: appendices and University of North Carolina at Charlotte, Friendly Russian, Chapter 1 Lesson 7.
• The Unicode Standard: Greek and Coptic and Cyrillic code charts.
• Minnesota Rules 7861.0210, Bingo, subpart 3: the B-I-N-G-O number ranges.
• W3C, Web Content Accessibility Guidelines (WCAG) 2.2, Success Criteria 2.2.2 Pause, Stop, Hide and 2.3.3 Animation from Interactions.

Reviewed by microplugins · Last updated October 2026