Protein pI calculator

Calculate the isoelectric point (pI) of protein sequences. Upload a FASTA file or paste your protein sequences below to get the pI values.

Input (Protein sequences)

FASTA

Click to upload or drag and drop

FASTA file (.fasta, .fas, .fa, .txt)

Max size: 50MB

Calculation options

Different pKa datasets may give slightly different pI values

Higher precision takes longer but gives more accurate results

Isoelectric point (pI)

Numbers

About isoelectric point (pI) calculation

The isoelectric point is the pH at which a protein has no net electric charge:

  • • Method: Henderson-Hasselbalch equation with bisection
  • • Charged residues: N/C termini, K, R, H, D, E, C, Y
  • • pKa values: From literature datasets (Bjellqvist recommended)
  • • Range: Typically between pH 4-12 for most proteins