ResidueBench
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Net Charge Calculator

See how the theoretical net charge of a peptide or protein changes with pH. Use the curve to inspect a specific pH or read the table for whole-number values. The model includes both free termini and ionizable side chains.

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Sequence input

Paste plain text or one FASTA record with up to 10,000 standard amino acid residues and 100,000 input code units. Calculation runs in your browser.

Results

Enter a valid sequence to plot its theoretical net charge.

How net charge is calculated

The calculator uses the same Bjellqvist pKa values and Henderson–Hasselbalch charge equation as the isoelectric point tool. It samples pH 0 to 14 in 0.1-unit steps and reports charge in elementary charge units (e).

Read the calculation method →

Worked example

INGAR

At pH 7.0, INGAR has a theoretical net charge of 0.7601 e using the Bjellqvist model.

Limitations

  • One linear, unmodified chain with free N and C termini and reduced cysteines.
  • Fixed pKa values approximate independent ionization. Structure, solvent conditions, and neighboring charges can shift experimental pI.
  • Treat short-peptide estimates with care because sequence context can have a large effect on ionization.
  • The graph ends at pH 14. Very basic sequences may stay positive throughout the displayed range.

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