Example 1
- Encode
- n = 1
- ABC
BCD
What does ABC become at shift 1? BCD.
Caesar Cipher
The calculator shifts each A–Z letter by n places. ABC at 1 gives BCD. HELLO at 3 gives KHOOR. This is not Morse code.
Dots and dashes are on the Morse code translator. A character number is on ASCII and Unicode.
Result
Enter a shift and text. The result will appear here.
How it works
The calculator shifts each A–Z letter by n places in the Latin alphabet. ABC at 1 gives BCD.
HELLO at 3 gives KHOOR. Decoding KHOOR at 3 returns HELLO.
After Z the alphabet wraps to A, so XYZ at 3 gives ABC. 29 is the same as 3, because 29 modulo 26 is 3.
A space stays a space. The calculator does not accept a digit or a Polish letter. This is not Morse.
Lowercase stays lowercase: abc at 1 is bcd.
A negative n moves backward. −1 from BCD gives ABC.
Formula
E(x) = (x + n) mod 26, D(x) = (x − n) mod 26
x is the letter position from 0 (A) to 25 (Z). n is an integer.
How to use
- Choose encode and enter shift 1.
- In the text field enter ABC and calculate. The result is BCD.
- To get KHOOR, change n to 3 and the text to HELLO.
- To get HELLO back, choose decode, keep 3, and paste KHOOR.
HELLO at 3 is KHOOR
That is the classic Caesar shift. n = 3.
- BCD
- ABC at n = 1.
- KHOOR
- HELLO at n = 3.
- ABC
- XYZ at n = 3, after the alphabet wraps.
Examples
Example 2
- Encode
- n = 3
- HELLO
KHOOR
What does HELLO become at shift 3? KHOOR.
Example 3
- Decode
- n = 3
- KHOOR
HELLO
What comes back from KHOOR at shift 3 backward? HELLO.
Related calculators
Frequently asked questions
What does ABC become at shift 1?
BCD. A goes to B, B to C, C to D.
What does HELLO become at shift 3?
KHOOR. That is the classic +3. H→K, E→H, L→O, O→R.
What comes back from KHOOR at shift 3 backward?
HELLO. Decode subtracts the same n.
What about XYZ at shift 3?
ABC. After Z the alphabet wraps to A.
Is 29 a different cipher than 3?
No. 29 modulo 26 is 3. The result is the same.
Does a space shift?
No. A space stays a space. Only A–Z letters move.
Does the calculator shift Ą or the digit 5?
No. This page uses the Latin A–Z alphabet. Polish letters and digits are not here.
Is this Morse?
No. Morse turns a letter into dots and dashes. Here the letter stays a letter, only shifted.
Do lowercase letters stay lowercase?
Yes. abc at 1 gives bcd. Case does not change.
Does a negative n work?
Yes. −1 from BCD gives ABC. That is the same as decode at 1.
What if I do not know the shift?
Under the result there is a list of 26 subtractions from the same text. You look for the sentence that makes sense.
Sources
The Caesar cipher is a shift modulo 26. The classic n is 3.
Page updated in 2026.