What it calculates
Sequence length, amino acid composition, average and monoisotopic molecular weight, net charge estimate, GRAVY hydropathy and 280 nm extinction coefficient.
Tools
Peptide Calculator: Molecular Weight, Sequence and Composition
Analyze peptide sequences: molecular weight, amino acid composition, one-letter and three-letter conversion, net charge, GRAVY and extinction estimates.
Live now
Sequence analysis tool
Paste a peptide sequence to estimate basic chemistry properties and convert between one-letter and three-letter amino acid notation.
Sequence chemistry
Peptide sequence calculator
Accepted formats
One-letter sequences like ACDEFGHIK, or three-letter tokens like Ala-Gly-Ser. Unknown or ambiguous residues are ignored and flagged.
Ignored unknown tokens: ACDEFGHIKLMNPQRSTVWY
Residues
0
Average mass
0.00 Da
Mono mass
0.00 Da
Net charge at pH 7.0
0.00
GRAVY hydropathy
0.00
Positive values are more hydrophobic on the Kyte-Doolittle scale.
Extinction coefficient
0 M-1 cm-1
Reduced estimate at 280 nm from Trp and Tyr.
Converted sequence
No valid residues yet
Three-letter output appears here.
Composition
A0
Ala
R0
Arg
N0
Asn
D0
Asp
C0
Cys
E0
Glu
Q0
Gln
G0
Gly
H0
His
I0
Ile
L0
Leu
K0
Lys
M0
Met
F0
Phe
P0
Pro
S0
Ser
T0
Thr
W0
Trp
Y0
Tyr
V0
Val
Property groups
- Hydrophobic
- Polar
- Acidic
- Basic
- Special
Calculation notes
- Mass assumes a linear peptide with free N- and C-termini.
- Modified residues, salts, labels and terminal caps are not included.
- Charge is a Henderson-Hasselbalch estimate, not a measured pI.
- Oxidized extinction estimate would be 0 M-1 cm-1 if cysteine pairs form cystines.
Best for
Quick peptide chemistry checks, glossary support, sequence notation conversion and educational research notes.
Common searches
Peptide molecular weight calculator, peptide sequence calculator, amino acid composition calculator and peptide hydropathy tool.
Important limitations
This calculator assumes the standard 20 amino acids in a linear peptide with free termini. It does not include terminal capping, amidation, acetylation, salts, counterions, glycosylation, isotope labels, non-standard residues or confirmed disulfide mapping.
Amino acid code table
The calculator accepts one-letter sequences like ACDE and three-letter tokens like Ala-Cys-Asp-Glu.
| 1-letter | 3-letter | Amino acid |
|---|---|---|
| A | Ala | Alanine |
| R | Arg | Arginine |
| N | Asn | Asparagine |
| D | Asp | Aspartic acid |
| C | Cys | Cysteine |
| E | Glu | Glutamic acid |
| Q | Gln | Glutamine |
| G | Gly | Glycine |
| H | His | Histidine |
| I | Ile | Isoleucine |
| L | Leu | Leucine |
| K | Lys | Lysine |
| M | Met | Methionine |
| F | Phe | Phenylalanine |
| P | Pro | Proline |
| S | Ser | Serine |
| T | Thr | Threonine |
| W | Trp | Tryptophan |
| Y | Tyr | Tyrosine |
| V | Val | Valine |
How mass is calculated
A peptide sequence is treated as a chain of amino acid residues. The tool sums residue masses, then adds one water molecule to represent the free termini of a simple linear peptide.
That is a useful educational estimate, but it is not a substitute for analytical testing. Terminal caps, salts, disulfides, labels and non-standard amino acids change the actual mass.
Peptide chemistry calculator FAQ
How is peptide molecular weight calculated?
The calculator sums amino acid residue masses and adds one water molecule for a linear peptide with free N- and C-termini. Modified residues, salts and terminal caps are not included.
What is the difference between average and monoisotopic mass?
Average mass uses natural isotope abundance averages. Monoisotopic mass uses the most abundant isotope of each element and is often used in mass spectrometry contexts.
What does GRAVY mean?
GRAVY is the grand average of hydropathy. Positive values indicate a more hydrophobic sequence on the Kyte-Doolittle scale, while negative values indicate a more hydrophilic sequence.
Can this calculator handle modified peptides?
No. It is limited to the standard 20 amino acids in a simple linear sequence. It does not include amidation, acetylation, PEGylation, labels, salts, disulfide mapping or non-standard residues.
Use with other peptide calculators
Pair sequence chemistry with concentration, unit conversion and accumulation tools when building research notes.
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Research & educational purposes only
The information on PeptideStat is for educational and research purposes only and is not medical advice. Many peptides discussed are research compounds not approved for human use. Always consult a qualified healthcare professional before making any health decisions. Articles may contain affiliate links — we may earn a commission at no extra cost to you.