Peptide Calculator

This peptide calculator page enables you to convert three-letter amino acid codes into one-letter codes and calculate key peptide properties. You can input a peptide sequence and compute parameters like length, molecular weight, hydropathy plot, and approximate volume.

Amino Acid Table (Click to expand)

Amino Acid	3-Letter Code	1-Letter Code
Alanine	Ala	A
Cysteine	Cys	C
Aspartate	Asp	D
Glutamate	Glu	E
Phenylalanine	Phe	F
Glycine	Gly	G
Histidine	His	H
Isoleucine	Ile	I
Lysine	Lys	K
Lysine	Lys	K
Leucine	Leu	L
Methionine	Met	M

Amino Acid	3-Letter Code	1-Letter Code
Asparagine	Asn	N
Proline	Pro	P
Glutamine	Gln	Q
Arginine	Arg	R
Serine	Ser	S
Threonine	The	T
Valine	Val	V
Tryptophan	Trp	W
Tyrosine	Tyr	Y
Asaragine	Asx	B
Glutamine	Glx	Z

Three to One Letter Converter: Select the amino acids from the dropdown list to build your peptide.

After you finish selecting amino acids to build your peptide, please select the blank option (the first empty value in the dropdown) to prevent duplicating the last chosen amino acid.


Hydropathy Plot Window size:
Length: Residues... Molecular Weight: g/mol	Extinction Coefficient: cm^-1 M^-1 Approximate Volume: A³
Three letter code:

Hydropathy Plot: This analysis graphically represents the distribution of hydrophobic and hydrophilic regions within your peptide. It is generated using a sliding window method (adjustable window size) that averages hydrophobicity over segments of the sequence.

Extinction Coefficient: This value estimates the peptide's ability to absorb light at 280 nm, based on the presence of aromatic amino acids such as tryptophan, tyrosine, and cysteine. Note that it may not be calculated if these residues are absent, and its result can sometimes depend on the window size.

Approximate Volume: This calculation provides an estimate of the total volume occupied by the peptide, derived from the summed volumes of its constituent amino acids. It offers a rough idea of the peptide's physical size.

This page was last updated: 6 March 2025.