One-to-Three Converter

Convert one-letter amino acid sequences to three-letter codes with customizable formatting.

Input

Protein sequence input

Output case

Output delimiter

Preserve FASTA format

Amino acids per line

Show position numbers

Output

Configure inputs to begin

Set options on the left, then click “Convert”.

What is one-to-three (amino acid conversion)?

"One-to-three" conversion refers to the process of translating a single-letter amino acid code into its three-letter abbreviation. This is a common practice in bioinformatics and biochemistry for interpreting and representing protein sequences.

Protein sequencing: Proteins are made of long chains of amino acids. These chains are represented in text format using abbreviations for each amino acid.
Convenience vs. clarity: The one-letter code is a compact and efficient way to write long protein sequences, while the three-letter code is often used for clarity, especially in a clinical or educational context.
Specialized tools: Many online tools and software applications perform this conversion. A user can paste a raw protein sequence (e.g., KVFGRCEL...) into a text box, and the tool will automatically convert it into the three-letter format (e.g., Lys Val Phe Gly Arg...).

One-to-three conversion table

The table below lists the standard one-letter and three-letter codes for the 20 common amino acids.

Amino acid	One-letter code	Three-letter code
Alanine	A	Ala
Arginine	R	Arg
Asparagine	N	Asn
Aspartic acid	D	Asp
Asparagine or Aspartic acid*	B	Asx
Cysteine	C	Cys
Glutamic acid	E	Glu
Glutamine	Q	Gln
Glutamine or Glutamic acid*	Z	Glx
Glycine	G	Gly
Histidine	H	His
Isoleucine	I	Ile
Leucine	L	Leu
Lysine	K	Lys
Methionine	M	Met
Phenylalanine	F	Phe
Proline	P	Pro
Serine	S	Ser
Threonine	T	Thr
Tryptophan	W	Trp
Tyrosine	Y	Tyr
Valine	V	Val
Unknown*	X	Xaa

Note: The special codes 'B', 'Z', and 'X' represent ambiguous amino acids.

Related tools

CSV to FASTA

Convert CSV and TSV files containing sequence data to FASTA format with flexible column mapping and automatic delimiter detection

PDB to FASTA converter

Convert Protein Data Bank files to FASTA sequence format

Three-to-one converter

Convert three-letter amino acid codes to single-letter codes

TXT to FASTA converter

Convert TXT or plain text sequences into FASTA format files for DNA, RNA, and protein workflows with cleanup, validation, and downloads

DNA to Protein Converter

Translate DNA sequences to protein sequences using genetic code

PDB to CIF Converter

Convert Protein Data Bank files to Crystallographic Information File format

PDB to MOL2 Converter

Convert Protein Data Bank files to MOL2 molecular format

Protein to DNA converter

Reverse translate protein sequences to possible DNA sequences

GenBank Feature Extractor

Extract sequence features (CDS, mRNA, gene, etc.) from GenBank files in FASTA format with support for spliced features

FASTA to FASTQ Converter

Convert FASTA sequence files to FASTQ format with mock quality scores

What is one-to-three (amino acid conversion)?

Protein sequencing: Proteins are made of long chains of amino acids. These chains are represented in text format using abbreviations for each amino acid.
Convenience vs. clarity: The one-letter code is a compact and efficient way to write long protein sequences, while the three-letter code is often used for clarity, especially in a clinical or educational context.
Specialized tools: Many online tools and software applications perform this conversion. A user can paste a raw protein sequence (e.g., KVFGRCEL...) into a text box, and the tool will automatically convert it into the three-letter format (e.g., Lys Val Phe Gly Arg...).

One-to-three conversion table

The table below lists the standard one-letter and three-letter codes for the 20 common amino acids.

Amino acid	One-letter code	Three-letter code
Alanine	A	Ala
Arginine	R	Arg
Asparagine	N	Asn
Aspartic acid	D	Asp
Asparagine or Aspartic acid*	B	Asx
Cysteine	C	Cys
Glutamic acid	E	Glu
Glutamine	Q	Gln
Glutamine or Glutamic acid*	Z	Glx
Glycine	G	Gly
Histidine	H	His
Isoleucine	I	Ile
Leucine	L	Leu
Lysine	K	Lys
Methionine	M	Met
Phenylalanine	F	Phe
Proline	P	Pro
Serine	S	Ser
Threonine	T	Thr
Tryptophan	W	Trp
Tyrosine	Y	Tyr
Valine	V	Val
Unknown*	X	Xaa

Note: The special codes 'B', 'Z', and 'X' represent ambiguous amino acids.