Letters to Numbers Calculator - A1Z26, T9, and Reversed Alphabet Codes

A letters to numbers calculator turns any text into the numeric code that each letter maps to under a chosen letter-to-number system. The default A1Z26 cipher assigns A=1, B=2, and so on up to Z=26, and the same tool also covers A0Z25, the reversed alphabet (A=26, Z=1), and the T9 phone keypad mapping.

• • Solve geocaching and ARG puzzle clues: Decode or encode the A1Z26 cipher numbers in geocache listings, escape rooms, and alternate-reality game handouts.
• • Build a phoneword from a name: Turn a vanity phrase such as BIRTHDAY into the digit string 24784329 so the matching phone number can be reserved.
• • Teach positional alphabets in the classroom: Show students how A1Z26, A0Z25, and a reversed alphabet produce different numbers for the same letter.
• • Draft letter-to-number ciphers for stories: Generate consistent letter-to-number tables for a short story, board game, or classroom handout.

Letter-to-number mapping has been used in classrooms and puzzle caches for more than a century. The A1Z26 form is the most common because it lines up with how teachers count the alphabet, and it gives a 0 token to spaces.

If you need the byte-level code points (decimal, hex, binary) for the same string rather than the letter position, the ASCII Converter works at the code-point level and accepts the same case-insensitive text input.

The calculator walks the input character by character, uppercases each letter, and applies the mapping that matches the selected mode. The result is a list of per-letter numbers joined by the chosen separator.

• inputText: The text to encode. Each Latin letter is processed independently.
• encodingMode: One of four encoding systems: A1Z26, A0Z25, reversed alphabet, or T9 phone keypad.
• separator: Token separator between per-letter numbers: space, comma, or no separator.

Every encoded token comes from one letter, so the encoded output length equals the number of letters plus any space tokens the mode inserts. Non-Latin letters and emoji are skipped in every mode and listed in the warnings row.

This calculator stops at the four letter-level systems. The full ASCII, hexadecimal, and binary forms live in the dedicated ASCII converter at the byte level.

According to ITU-T Recommendation E.161, the international telephone keypad assigns the letters ABC to 2, DEF to 3, GHI to 4, JKL to 5, MNO to 6, PQRS to 7, TUV to 8, and WXYZ to 9

When the encoded list needs to land in 8-bit binary rather than decimal A1Z26 tokens, the Text to Binary Converter page gives you the binary representation of each ASCII code on a single base.

Four short ideas cover every result the calculator shows, and each one feeds directly into the per-letter mapping.

These four ideas cover every encoding mode on this calculator. Switching between them is just a different function of the same letter.

For the byte-level view of the same string, the dedicated ASCII converter works at the code-point level.

For the underlying base-2 logic that powers binary encoding of letters, the Binary Converter walks through the same positional math the A1Z26 cipher uses, but on the digit 0 and 1 instead of the Latin alphabet.

Five quick steps turn any text into a per-letter number list, with a separator you control and a warnings row.

1. 1 Type or paste the text: Enter any text in the Text to Encode field. Letters can be uppercase or lowercase.
2. 2 Pick the encoding mode: Choose A1Z26, A0Z25, reversed alphabet, or T9 phone keypad.
3. 3 Choose the token separator: Use space, comma, or no separator to glue digits into a phone number.
4. 4 Read the encoded list: The encoded number list updates as you type.
5. 5 Check the counts and warnings row: Letter count, character count, and skipped count tell you how much was encoded.

Type BIRTHDAY, set mode to T9 phone keypad, separator to none. The encoded list becomes 24784329. Switch to A1Z26 and the same word becomes 2 9 18 20 8 4 1 25.

If the puzzle clue you are decoding needs a Caesar shift rather than a flat A1Z26 lookup, the Caesar Cipher Shifter page handles the rotated alphabet the same way A1Z26 handles the unrotated one.

A purpose-built letters to numbers calculator keeps the four encoding systems consistent and makes it obvious when a character was skipped.

• • Four encoding systems in one tool: A1Z26, A0Z25, reversed alphabet, and T9 phone keypad all sit behind one mode selector.
• • Case-insensitive letter matching: Uppercase and lowercase letters encode to the same list.
• • Separator control for paste-ready output: Choose space, comma, or no separator so the encoded list drops into a clue sheet or phoneword generator.
• • Visible character and letter counts: Letter count, character count, and skipped count are reported on the result panel.
• • Skipped characters are named, not hidden: Every skipped character is listed in the warnings row with its position and a short reason.

When the same string needs to land in a different base, the dedicated ASCII converter works at the byte level rather than the letter-position level. For inputs that contain binary or hexadecimal digits, the change of base calculator handles the digit-level conversion.

If you want each A1Z26 token written in a different number base without re-encoding the text, the Change of Base Calculator converts the same numeric values between binary, octal, decimal, and hex so the letter-to-number mapping stays the single source of truth.

Three variables change the encoded list and two limitations tell you when to switch to a different tool.

• • The four modes only cover the 26 Latin letters. Accented characters, CJK characters, emoji, and other code points outside A-Z are not part of A1Z26, A0Z25, or reversed alphabets.
• • T9 mode produces a digit string shorter than the input and ambiguous between many words. BIRTHDAY = 24784329 is the same digit string you would get from AIRTHDAY, so the mapping is many-to-one and not a true cipher.

If you only need the binary bit pattern of each ASCII code rather than the letter position, the text-to-binary converter gives you the 8-bit representation of each character on a single base.

According to dCode's A1Z26 cipher page, the A1Z26 cipher assigns each Latin letter its 1-based position in the alphabet (A=1 through Z=26) and treats a space as 0, which is the most common letter-to-number convention for geocaching clue sheets and ARG puzzles

If the puzzle you are encoding uses a reversed alphabet and you also need the right-to-left mirror of the text itself, the Mirror Text Converter page produces the mirrored string so the two transformations stay consistent.