Letter-to-Number Codes

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Each letter is replaced by its position in the alphabet.

Letter-to-number coding is the simplest substitution cipher. Each letter is replaced by its position in the alphabet: A=1, B=2, C=3, and so on up to Z=26. To decode, convert each number back to its corresponding letter. This is often the first code type introduced in aptitude tests.

A=1, B=2, C=3, ... Z=26

• CAT = 3-1-20
• HELLO = 8-5-12-12-15
• 3-15-4-5 = CODE

How to recognize it

• Numbers 1-26 (no numbers higher than 26)
• Pattern follows alphabetical position
• Often separated by hyphens or spaces

Common mistakes

• Confusing letter positions (common: J=10, not 11)
• Forgetting alphabet order mid-word
• Not recognizing double-digit numbers (12 is L, not 1-2)

Practice guidance

Coding & Decoding