Protein isoelectric point calculator

Isoelectric point, the pH at which a particular molecule carries no net electrical charge, is an critical parameter for many analytical biochemistry and proteomics techniques, especially for 2D gel electrophoresis (2D-PAGE), capillary isoelectric focusing (cIEF), X-ray crystallography and liquid chromatography–mass spectrometry (LC-MS)

IPC 2.0 based on deep learning is available at

Below is the text area where you can paste amino acid sequence of analyzed protein (peptide) or multiple sequences in fasta format

  • Input should be ONE sequence in plain text or MULTIPLE sequences in FASTA format (limit is set to 50,000 chars)
  • Input should be in one letter amino acid code, input can be upper or lower case.
  • All non-amino acid characters will be removed from the sequence.
  • For big datasets use standalone version or split your input into 50k chunks.
Input example: for Ala-Pro-Lys-His-Ala-Tyr peptide, please enter APKHAY
Standalone version of the program
IPC in Python
(command line, any OS)

Available also as PyPi package (pip install isoelectric)

Reference: Kozlowski LP (2016) IPC - Isoelectric Point Calculator. Biology Direct 11:55.

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License: IPC is public domain, for details see license
IPC website mirrors: Mirror 1 Mirror 2

If you are interested in high-throughput analysis of isoelectric points for whole organisms you might want to check this database:
Proteome-pI - Proteome Isoelectric Point Database - predicted isoelectric point for ~21 million proteins across 5,029 organisms

Contact: Lukasz P. Kozlowski