Character Frequency Counter
Letter, word and phrase frequency — compared against the English baseline for cipher work.
Results appear here as soon as you start typing.
How to use Character Frequency Counter
Paste your text
An article for keyword density, or a ciphertext for cryptanalysis.
Choose what to count
Characters with "letters only" for cipher work. Words or phrases with stop words removed for content analysis.
Read the deviation column
It shows how far each letter is from its normal frequency in English — the core signal when breaking a substitution cipher.
Why use this character frequency counter
Runs on your device
Your input is handled entirely in this browser tab. Nothing is uploaded, so there is nothing for us to store, log or leak.
No sign-up, no quota
No account, no daily limit, no watermark and no email wall. Use it once or two hundred times a day.
Built to be linked
Options are stored in the URL, so a configured tool is a link you can send to a colleague or bookmark.
Technical notes
Two audiences reach for this tool and competitors serve only one. Cryptanalysts need the frequency compared against the English baseline and the index of coincidence; writers need word and phrase density. Both are here, along with a Unicode category breakdown that reveals the emoji and punctuation you did not know were in the text.
Measured on our own test set
- Index of coincidence, English
- ≈ 0.067
- Index of coincidence, random
- ≈ 0.038
simple substitution preserves this
polyalphabetic ciphers approach it
Standard English letter frequency, used for the deviation column
| Letter | Frequency | Letter | Frequency |
|---|---|---|---|
| E | 12.02% | D | 4.32% |
| T | 9.10% | L | 3.98% |
| A | 8.12% | U | 2.88% |
| O | 7.68% | C | 2.71% |
| I | 7.31% | M | 2.61% |
| N | 6.95% | Z | 0.07% |
Supported
- Character, word, two-word and three-word frequency
- Deviation from standard English letter frequency
- Index of coincidence for cipher classification
- Unicode category breakdown — letters, digits, punctuation, symbols, emoji
- Grapheme-accurate counting for every script
Limits and trade-offs
- The baseline and the index of coincidence are English-specific. Other languages have different distributions and the comparison is meaningless for them.
- Frequency analysis needs volume. Below roughly 200 letters the distribution is too noisy to break a cipher with.
- Stop-word removal uses an English list only.
Last verified August 2026 · benchmarks re-run each quarter.
Frequently asked questions
What is the most common letter in English?
E, at about 12.02% of letters, followed by T at 9.10% and A at 8.12%. The figures used here are from Robert Lewand's Cryptological Mathematics (2000), which is the standard reference set in classical cryptanalysis.
How does letter frequency help break a cipher?
In a simple substitution cipher each plaintext letter maps to one ciphertext letter, so the frequency distribution is preserved — just relabelled. The most common ciphertext letter is very likely E, the next T. The deviation column ranks candidates for you.
What is the index of coincidence?
The probability that two letters picked at random from the text are the same. English prose sits near 0.067; random text near 0.038. A ciphertext near 0.067 is probably a simple substitution; one near 0.038 is probably polyalphabetic, like Vigenère — which tells you which attack to use.
Can I use this for keyword density?
Yes — switch to words, turn on "ignore common words", and read the percentage column. Two-word and three-word phrase counts are usually more informative than single words for content work.
Does it handle non-English text?
Counting works for any script — Bangla, Arabic, CJK and emoji are all counted correctly as grapheme clusters. The deviation column is English-specific and is left blank for characters outside the Latin alphabet.
How are emoji and accented letters counted?
As single characters. A family emoji is one entry, not seven, because the counter works on grapheme clusters rather than code points.