Double letters: which ones double, and which never do
39,374 words in our dictionary — 23.4% of the whole list — contain a doubled letter: the same letter written twice in a row. Some letters double constantly; a couple never double at all. This is the mirror image of our isograms guide, where no letter is allowed to repeat at all — and of our alphabetical-order guide, since a word whose letters strictly increase can never repeat one either.
Doubling gets more likely as words grow
The share of words containing a doubled letter rises steadily with length, from 2.1% at 2 letters to 37.3% at 15, the far end of our range. The highest share at any length is 37.3%:
| Length | Share with a doubled letter |
|---|---|
| 2 letters | 2% |
| 3 letters | 5% |
| 4 letters | 10% |
| 5 letters | 13% |
| 6 letters | 18% |
| 7 letters | 22% |
| 8 letters | 23% |
| 9 letters | 24% |
| 10 letters | 25% |
| 11 letters | 26% |
| 12 letters | 29% |
| 13 letters | 30% |
| 14 letters | 35% |
| 15 letters | 37% |
Which letters double most
Counting every word that contains a letter doubled at least once, as a share of the full 168,401-word dictionary:
Which letters never double
Searching the whole dictionary for a doubled letter, 2 never turn up at all: QQ, XX appear in no word in our list.
Two endings do most of the work
3,690 words end in a doubled S — 2.2% of the dictionary — and 405 end in a doubled L, 0.2%. -NESS alone accounts for 2,677 of the doubled-S words and -LESS for 646; on the L side, -ILL accounts for 112. Those suffixes are a big part of why S and L lead the chart above by such a distance.
How pairs stack up
Most words with a doubled letter have exactly one such pair. A second doubled pair in the same word is rarer, and a third rarer still:
| Doubled pairs | Words |
|---|---|
| 1 pair | 36,616 |
| 2 pairs | 2,650 |
| 3 pairs | 108 |
Common, everyday examples of the one-pair case:
And common examples of the two-pair case, 2,650 words strong against the 108 that reach three:
The rarest doublers
Setting aside Q, X, which never double at all, the letters that come closest without quite managing it are Y, J, W, V, U. Y doubles in only 2 words in the whole dictionary, against the thousands managed by S and L at the top of the chart.
Words with the most doubled pairs
Counting non-overlapping doubled pairs in each word, the most found anywhere in our dictionary is 3. 108 words reach that maximum, common ones first:
The pattern behind most of the list is long, suffix-heavy words — -NESS, -LESS and -EE endings pile doubled letters onto an already-doubled root.
Elsewhere on the site
Doubled letters are one slice of a bigger picture about how English words are built — the full letter-frequency guide covers every letter's overall share. Test any rack against the word unscrambler, or browse a length in full on the words-by-length hub.