Letters to numbers, alphabet to numbers and back.

Letters to numbers means replacing each letter with a number. The usual way is A1Z26: A is 1, B is 2, and so on to Z, which is 26. It is a substitution code, not secret writing, because anyone can reverse it with the same table. This page does it in both directions, with a few other numbering schemes, and lets you set the separator, the treatment of spaces and punctuation, and the case. It is a plain lookup. It makes no claim about what the numbers mean.

How to use it

1. Leave Letters to numbers selected and type in Your text. The numbers appear on the right as you type.
2. Choose Number each letter by: place in the alphabet, ASCII or Unicode code, phone keypad digit, or phone keypad multi-tap.
3. For place in the alphabet, pick a Numbering: A1Z26, A0Z25, or one of the two reversed options.
4. Set the Separator and what A space becomes. Tick Two digits each if you want 01 to 26 in a run.
5. To go back, choose Numbers to letters and paste the numbers, or press Use the result as the new input to flip what you just made.
6. Press Copy for the result, or Copy link for a link with your text and settings.

Worked example: Hello world

H is the 8th letter, E the 5th, L the 12th and O the 15th, so Hello is 8 5 12 12 15. World is 23 15 18 12 4. With a slash for the space, the full result is 8 5 12 12 15 / 23 15 18 12 4. The numbers add up to 124, which the Total card shows as plain arithmetic.

The numbering options

The reversed numbers count from the end of the alphabet, which is what an Atbash-style reversed alphabet does when it pairs A with Z. A reversed number is 27 minus the normal one, so H is 19.

ASCII and Unicode codes

Computers store each character as a number. In ASCII, capital A is 65 and lower case a is 97, so the case changes the number here. Hi is 72 105 in decimal, 48 69 in hex and 01001000 01101001 in binary. This mode numbers every character, spaces and punctuation too. It can also read the codes back to text. For whole sentences in binary, the binary translator shows the bytes of any text.

Phone keypad numbers

On a phone keypad the letters share keys: 2 has ABC, 3 has DEF, 4 has GHI, 5 has JKL, 6 has MNO, 7 has PQRS, 8 has TUV and 9 has WXYZ. This is the arrangement in ITU-T Recommendation E.161 (02/2001), checked 18 Oct 2026. The keypad digit mode writes one digit per letter, so Hello is 4 3 5 5 6. Since one digit stands for several letters, that cannot be read back to a single word. Multi-tap fixes this by pressing the key once for the first letter, twice for the second, and so on: Hello is 44 33 555 555 666. Multi-tap can be read back when the letters are separated, and a 0 is read as a space.

Reading numbers back

Pick Numbers to letters and paste numbers separated by spaces, commas or dashes. A slash or a bar becomes a space, and a 0 does too if you chose a zero for spaces. A number outside the range, such as 27 in A1Z26, shows as a question mark and is listed under the result. When the numbers run together, as in 0805121215, tick Two digits each so they are read in pairs.

Working out which code you have

If you are decoding a puzzle, look at the range of the numbers. Every number from 1 to 26 points to A1Z26, and a 0 in the list points to A0Z25 or the reversed zero version. Numbers from 65 to 90 are capital letters in ASCII, and 97 to 122 are lower case. Groups of eight ones and zeros are binary ASCII, and pairs of hex digits from 41 to 5A are capitals. Runs of the same digit, such as 44 or 555, point to multi-tap. Try each choice under Number each letter by, and the one that gives readable words is the one used.

Common problems

• The numbers run together. 1 12 and 11 2 would both be 1112 with no separator. Use a separator or two-digit numbers.
• Digits in the text. A digit typed in the text stays a digit, so R2D2 gives 18 2 4 2. You cannot tell the digits from letter numbers when reading it back. Choose Leave them out if that matters.
• Other alphabets. Only A to Z get numbers in the alphabet mode. Letters such as Greek or Cyrillic are kept as typed and counted in the status line. Use ASCII or Unicode codes to give every character a number.

For dots and dashes instead of numbers, see the Morse code translator.