ConverterHub

Tap Code Translator

Choose a direction and enter text or dot groups to translate tap code.

How it is calculated

The tool uses a 5×5 grid filled row by row with 25 letters, K sharing the cell of C: row 1 A B C D E, row 2 F G H I J, row 3 L M N O P, row 4 Q R S T U, row 5 V W X Y Z. Each letter becomes two groups of dots, first the row number, then the column number, for example B is row 1, column 2, so . ... In encode mode letters are separated by / , case is ignored, and spaces, digits and punctuation are dropped. In decode mode, each letter must be two dot groups separated by a space, and letters separated by /; each group may have 1 to 5 dots. The output is upper case, and a K always comes back as C.

Worked example

Encode HELP. Step 1: H is in row 2, column 3, written .. .... Step 2: E is row 1, column 5, . ...... Step 3: L is row 3, column 1, ... .. Step 4: P is row 3, column 5, ... ...... The tool joins them as .. ... / . ..... / ... . / ... ...... Pasting this string into decode mode returns HELP. The dots map to taps on a wall: a pause marks the move from row to column.

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Common mistakes

  • Looking for a separate K: K shares the cell of C, so "KICK" is encoded exactly like "CICC" and decodes with C, and the spelling has to be recovered from context.
  • Leaving out the slash between letters when decoding. A string such as .. ... . ..... does not decode; each letter needs to be written as two dot groups with / between letters.
  • Typing digits or punctuation and expecting them in the code. They are silently skipped, so "HELP 911" encodes only HELP.
  • Using groups of more than five dots or a zero-dot group, which cannot refer to a cell in the grid.
  • Starting the grid at A with K in its normal place (a layout used elsewhere) and then checking the result against it; here row 3 starts with L.

About this calculator

Tap code maps the 26-letter alphabet onto a 5×5 Polybius square by combining C and K into one cell, then encodes each letter as a pair of tap groups — one for its row, one for its column (for example, "B" sits at row 1, column 2, so it's tapped as one knock, then two knocks). Converting text runs each letter through that same row-column lookup, and decoding reverses it by counting the taps in each pair.

The code became famous as a way for prisoners of war — most notably American POWs held in Vietnam — to communicate silently through cell walls when spoken language and visible signals weren't possible. Today escape room designers, puzzle hobbyists, and cryptography enthusiasts use tap code translators like this one to build and solve puzzles based on the same historical cipher.

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