Translate letters to numbers
To translate letters in a string to numbers, you can use an array formula based on the TEXTJOIN and VLOOKUP functions, with a defined translation table to provide the necessary lookups. In the example shown, the formula in C5 is:
where "xtable" is the named range E5:F10.
Note: this is an array formula and must be entered with control + shift + enter.
How this formula works
At the core, this formula uses an array operation to generate an array of letters from the input text, translates each letter individually to a number, then joins all numbers together again and returns the output as a string.
To parse the input string into an array or letters, we use MID, ROW, LEN and INDIRECT functions like this:
LEN returns the length of the input text, which is concatenated to "1:" and handed off to INDIRECT as text. INDIRECT evaluates the text as a row reference, and the ROW function returns an array of numbers to MID:
MID then extracts one character for at each starting position and we have:
Essentially, we are asking VLOOKUP to find a match for "a", "b", and "c" at the same time. For obscure reasons, we need to "dereference" this array in a particular way using both the T and IF functions. After VLOOKUP runs, we have:
and TEXTJOIN returns the string "946". If you need a number as final result, add zero. The math operation will coerce the text into a number.
Note: the TEXTJOIN function was introduced via the Office 365 subscription program in 2018.