How this calculator works
The NATO phonetic alphabet gives every letter a word that is hard to confuse with another when spoken over a poor radio link. The spelling direction replaces each letter with its word, keeps digits as the standard spoken digits and leaves punctuation as it is. Letters inside a word are separated by spaces and separate words by a slash, so a listener knows where one word ends. The reverse direction reads each code word, case-insensitively, back into a character and joins the characters within a slash group into a word. Words it does not recognise are copied through unchanged, which makes partial or hand-written input easy to inspect.
Formula
Text to words: for each character, replace a letter with its NATO word (Alfa, Bravo, ... Zulu) and a digit with Zero to Niner; join characters in a word with spaces and words with " / ". Words to text: split on "/", then split each group on whitespace, map each recognised word back to its character and join.
Worked example
SOS becomes Sierra Oscar Sierra, because S is Sierra and O is Oscar. Reading Sierra Oscar Sierra back gives SOS. A two word message such as Go 2 becomes Golf Oscar / Two, and the slash marks where the second word starts.
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Frequently asked questions
Should I write Alfa or Alpha?
The international spelling used by NATO and ICAO is Alfa, chosen so that it is spelled the same way by speakers of different languages. Alpha is common in general writing but is not the official code word.
Why is Juliett spelled with two t?
The doubling is intentional. It helps French speakers, who may treat a final single t as silent, pronounce the word clearly. The same principle explains the unusual spelling of Alfa.
How are numbers read?
Digits use the spoken forms Zero to Niner, with Niner used instead of Nine to avoid confusion with the German word nein. The translator also accepts Nine when reading words back.
What happens to punctuation and accents?
Punctuation is passed through as its own token, and accented letters are not part of the alphabet, so they are copied unchanged. In the reverse direction, unrecognised words are left as typed so nothing is silently dropped.