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Caesar Cipher Shift Calculator

Work out caesar cipher shift instantly with clear inputs, formula shown and shareable results.

About Caesar Cipher Shift Calculator

The Caesar cipher shifts each letter a fixed number of positions modulo 26, leaving non-letters untouched. Its keyspace is just 25 usable shifts, so exhaustive search is instant, and frequency analysis identifies the shift from a single line of ciphertext. It survives as a teaching example of modular arithmetic and of why key size alone determines nothing if the keyspace is tiny.

Formula

Caesar shift

encrypt: c = (p + k) mod 26; decrypt: p = (c - k) mod 26, applied to letters only

Worked example

With the default values below, Caesar Cipher Shift Calculator returns Transformed text of Dwwdfn dw gdzq. Change any input above and every figure here is recalculated in your browser.

Inputs used

Text
Attack at dawn
Shift amountaccepts -25–25
3
Operationone of Encrypt (shift forward), Decrypt (shift back)
Encrypt (shift forward)

Results

Transformed text
Dwwdfn dw gdzq
Effective shift applied
3
Letters transformed
12
Possible keys
25

Step by step

  1. 1Values used
  2. 2Caesar shift
  3. 3Transformed text= Dwwdfn dw gdzq
  4. 4Effective shift applied= 3
  5. 5Letters transformed= 12
  6. 6Possible keys= 25

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What is ROT13?

A Caesar cipher with shift 13, which is its own inverse because 13 + 13 = 26. It is used to obscure spoilers, not for security.

How is a Caesar cipher broken?

Try all 25 shifts, or compare letter frequencies against the language's expected distribution. Both take seconds by hand.

Related Calculators

Caesar Cipher Shift Calculator – Calculate Transformed text