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Shannon Entropy Calculator

Shannon entropy (bits per symbol)

Client-side computation for analysis, verification, and learning. Do not paste production secrets into untrusted sites; prefer local tooling for key material.

Educational / engineering use. RSA mode uses tiny primes for illustration only—not for real key generation.

Sample string
Entropy
Alphabet size: 3
H (bits per symbol): 1.459148
Total bits if IID: 8.7549

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What is Shannon Entropy Calculator?

Calculates the average information content (uncertainty) in a data source, measured in bits. Higher entropy means more randomness useful in compression analysis, cryptography, and evaluating password strength.

Shannon Entropy Formula

H(X)=Σ(i=1..n)pilog2(pi)H(X) = −Σ(i=1..n) p_i log2(p_i)

Where p_i is probability of symbol i. Result in bits. For equal probabilities: H = log2(n).

Step-by-Step

  1. Count symbol frequencies.
  2. Convert counts to probabilities p_i.
  3. Compute p_i log2(p_i) for each symbol.
  4. Sum all terms.
  5. Negate the sum to get entropy in bits/symbol.

Worked Example

Input: "AABBC"

Frequencies:A=2,B=2,C=1(total5)Frequencies: A=2, B=2, C=1 (total 5)
Probabilities:pA=0.4,pB=0.4,pC=0.2Probabilities: pA=0.4, pB=0.4, pC=0.2
H=(0.4log2(0.4)+0.4log2(0.4)+0.2log2(0.2))H = -(0.4*log2(0.4) + 0.4*log2(0.4) + 0.2*log2(0.2))

≈ 1.522 bits.

Where Shannon Entropy Calculator Is Applied

  • Data compression algorithms (Huffman coding, ZIP)
  • Measuring password strength and randomness
  • Malware detection (high-entropy sections indicate packed/encrypted code)
  • Machine learning — decision tree splitting (information gain)
  • Cryptanalysis — identifying encryption strength
  • Image compression (JPEG, PNG optimization)
  • Network anomaly detection (traffic entropy analysis)

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