K Parameter Calculator

Calculate the K parameter for Karlin-Altschul statistics in BLAST E-value computation.

K parameter appears in the E-value formula: E = K × m × n × e^(-λS). It's typically around 0.04-0.13 for protein matrices.
K Parameter
0.041
Pre-exponential factor
Effective K
0.035
Adjusted for finite length
Alpha (α)
1.90
Finite-size parameter
Beta (β)
-3.0
Edge correction factor
K_eff = K × (1 - e^(-α×min(m,n)^β))

What is K Parameter Calculator?

K Parameter Calculator computes the Karlin-Altschul K value used in BLAST E-value calculations. Essential for determining statistical significance of sequence alignments.

How to Use This K Parameter Tool

  1. Select scoring matrix type
  2. Adjust lambda and entropy values
  3. View K parameter and corrections

When to Use

  • Computing BLAST E-values
  • Validating alignment significance
  • Custom scoring matrix development

Example Input

Matrix: BLOSUM62
λ = 0.267, H = 0.44

Try with your own parameters or use the Example button.

Example Output

K = 0.041
K_eff = 0.035

Results include K value and effective K for finite sequences.

FAQ

Q: What are typical K values?
A: Usually 0.04-0.13 for protein matrices, ~0.33 for DNA.

Q: What is K_effective?
A: K adjusted for finite sequence lengths using edge correction.