Peptide Calculator

Paste a one-letter amino acid sequence and get molecular weight, length, composition and an estimated net charge at pH 7.

Amino acid sequence (one-letter code)

Example: YGRKKRRQRRR (TAT peptide). Only A–Z letters are counted.

Termini form

How it works
Peptide mass = sum of residue masses + water (18.02 Da) for free termini.

Common masses: Gly 57.05 · Ala 71.08 · Leu/Ile 113.16 · Arg 156.19 · Trp 186.21. Cys may form disulfide bonds — subtract 2 Da per bond.

⚖️ Residue masses

Monoisotopic masses for all 20 AAs.

📊 Composition table

Full residue-by-residue breakdown.

🤵 Charge estimate

Rough net charge at physiological pH.

🔑 Termini options

Free, amidated or cyclic correction.

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