BOOKKEEPER is famous for one thing: three double letters in a row, OO, KK and EE. It turns out that is a very exclusive club. We counted every doubled letter in the JumbleFix word list to see how rare it really is, which letters like to double up, and which never do.
How common are double letters?
- 35,218 words have at least one double letter, 22.6% of the list.
- 33,120 have exactly one doubled pair.
- 2,022 have two doubled pairs, like ADDRESS and SUCCESS.
- 76 have three.
- None have four.
So about one word in five has a double letter, but three doubles in one word is a club of 76 members out of nearly 156,000.
Three in a row: the record holders
Only three words have three double letters back to back:
- BOOKKEEPER
- BOOKKEEPERS
- BOOKKEEPING
All three are the same word in different forms, which tells you how hard the trick is. It only works because BOOK ends in K and KEEP starts with one, so the join makes KK, with OO just before it and EE just after. Two ordinary words, glued together at exactly the right letter.
Three doubles, not in a row
Loosen the rule to three doubled pairs anywhere in the word and the club grows to 76. The shortest members:
- 7 letters: AARRGHH, a very committed scream.
- 8 letters: ALLOTTEE, APPELLEE, HEELLESS, KEELLESS, KEENNESS and TOOLLESS.
- 9 letters: seven words, including ADDRESSEE, ARROWWOOD, COMMITTEE and GREENNESS.
COMMITTEE is the everyday champion: MM, TT and EE in a word most people actually use. It is also a reliable spelling trap, which feels right, since it takes a committee to agree on that many letters.
Two doubles in a row
Two doubled pairs side by side is more common: 207 words do it. Familiar ones include COFFEE, TOFFEE, COOLLY and LESSEE. The pattern loves the ending -EE, which is why COFFEE, TOFFEE and LESSEE all qualify.
Which letters double the most
Some letters double constantly. Counting every doubled pair in the list:
- SS, 7,475 times
- LL, 7,240
- EE, 3,623
- OO, 3,557
- TT, 2,814
- RR, 2,145
- PP, 1,694
- NN, 1,501
- FF, 1,498
- MM, 1,455
SS and LL are far ahead of everything else, largely because of endings like -NESS, -LESS and -ALLY.
The rare doubles
At the other end, some letters almost never double:
- JJ appears in just 4 words: HAJJ, HAJJES, HAJJI and HAJJIS, from the pilgrimage to Mecca.
- YY appears in just 2: SAYYID and SAYYIDS.
- WW shows up in 19 words, including GLOWWORM, POWWOW and BOWWOW.
- UU shows up in 25, including VACUUM, CONTINUUM and MUUMUU, which manages it twice.
- VV shows up in 26, including SAVVY, CHIVVY, DIVVY and REVVED.
- HH shows up in 39, including WITHHOLD, FISHHOOK and BATHHOUSE.
- II shows up in 50, including SKIING and TAXIING.
And two letters never double at all: Q and X.
A triple, just once
Three of the same letter in a row is rarer still. Exactly one word in the list does it: BRRR, the sound of being very cold. You can add an R for every degree below freezing, but the dictionary stops at three.
Why doubles matter in word games
- Wordle: repeated letters are a common trap. Do not rule out a letter just because it is already green; words like EERIE and BOBBY use letters more than once.
- Spelling Bee: letters can be reused, so doubles make pangrams longer than seven letters. Our Spelling Bee guide has more on this.
- Scrabble: a standard set has only one J, so HAJJ cannot be played without a blank. Doubles of common letters like SS, LL and EE are easy to draw; doubles of rare letters usually need a blank.
To see every word you can make from a rack, double letters included, try the word unscrambler.
How we counted
We started from the ENABLE word list, a public-domain list used by many word games (172,823 words), and kept the 155,976 words that are also active on JumbleFix. A double letter is the same letter twice in a row. We counted the doubled pairs in each word, and the totals for each letter count every doubled pair across the list.
Written by Morty Leonid with AI assistance. Every count in this article comes from queries against the JumbleFix word list.