Amino Acid Lookup
Reference table of the 20 standard amino acids — 1-letter and 3-letter codes, names in your curriculum language, and the codons that code for each. Searchable. Curriculum-aligned.
Amino Acid Lookup
- Curriculum
- English (global) — Cambridge International + IB
- Built against
- Cambridge IGCSE Biology 0610 + IB Diploma (2023–2025) — Proteins & Amino Acids
- Unit system
- SI primary; US/imperial readout below
- First published
- 2 Jun 2026
- Last updated
- 4 Sep 2026
View authoritative scientific sources
- IUPAC-IUBMB — amino acid nomenclature
- NCBI — standard genetic code (translation table 1)
- Campbell Biology, 12th edition — proteins
- Amino acid — Encyclopædia Britannica
⚠️ Educational use only — see full disclaimer
EDUCATIONAL USE DISCLAIMER
This calculator is provided for educational and reference purposes only. It is not a substitute for instruction from a qualified teacher, your prescribed textbook, or your school's official curriculum materials.
When preparing for examinations, always cross-check our calculations and notation against your current syllabus and your teacher's guidance. Syllabus conventions and accepted notation vary between curricula and may change between examination years.
If you believe any calculation, notation, or curriculum reference in this tool is inaccurate, please let us know via the feedback button. We review feedback promptly and update tools when verified corrections are needed.
RECATOOLS accepts no liability for academic, examination, professional, or research outcomes arising from use of this tool.
How to Use the Amino Acid Table
Pick your curriculum
Use the curriculum pills above to match your syllabus (Cambridge/IB, 高考 or SBMPTN). Amino acid names and the whole page follow your selection.
Browse or search
The table lists the 20 standard amino acids. Type a code (Met or M) or a name to filter it.
Read the codes and codons
Each row shows the 1-letter code, the 3-letter code, the name, and the codons that code for that amino acid.
Check against your syllabus
The Tool Information block shows exactly which syllabus this is built against. Spot something off? Use the feedback button.
Amino Acids, in Your Curriculum's Words
There are 20 standard amino acids that build proteins. Each has two short codes that are international standards — a 1-letter code (e.g. M for methionine) and a 3-letter code (e.g. Met) — plus one or more mRNA codons that code for it. This table lists all three for every amino acid, with the full name shown in the language of the curriculum you select.
The 1-letter and 3-letter codes are international standards and the same across curricula, but the full names differ by language. Because the genetic code is degenerate, most amino acids are coded by more than one codon — leucine, for example, has six codons. All data stays in your browser; nothing is uploaded, and the tool works offline once loaded.
Just 20 amino acids, arranged in different orders, make up every protein in your body — from enzymes to muscle.
10 Facts About Amino Acids
There are 20 standard amino acids that build proteins.
Each has a standard 1-letter and 3-letter code.
Amino acids are joined by peptide bonds.
Methionine (Met) starts almost every protein chain.
Thanks to degeneracy, many amino acids have several codons.
Leucine has six codons — the most of any.
The human body cannot make the 9 essential amino acids.
Every amino acid has an amino and a carboxyl group.
The order of amino acids determines a protein's structure.
This table runs in your browser — no data is uploaded.
Frequently Asked Questions
- Both are international standard abbreviations for the same amino acid. The 3-letter code (e.g. Met, Gly) is easier to read and common in class, while the 1-letter code (e.g. M, G) saves space when writing long protein sequences. This table shows both for every amino acid.
- Because there are 64 codons but only 20 amino acids, most amino acids are coded by two to six codons. This property is called the degeneracy or redundancy of the genetic code, and it helps reduce the impact of some mutations.
- An essential amino acid is one the human body cannot make and so must obtain from food. There are nine essential amino acids for adult humans, including leucine, lysine and tryptophan. The rest are called non-essential because the body can synthesise them.
- Type in the search box: it can be the 1-letter code (M), the 3-letter code (Met), or part of its name in your curriculum language. The table filters live to show the matches.
- The 1-letter and 3-letter codes are IUPAC-IUBMB international standards and the same worldwide. The full names are translated into each language — "Glycine" in English is 甘氨酸 in Chinese and "Glisina" in Indonesian. This table switches the names by your curriculum but keeps the standard codes.
- No. This table lists only the 20 amino acids that build proteins. The three stop codons (UAA, UAG, UGA) code for no amino acid and are shown in the Genetic Code Table tool.
- The Tool Information block lists the exact syllabus for your selected curriculum (e.g. SBMPTN/SNBT Biologi). It is a study aid, not a substitute for your official syllabus or teacher.
- No. All data loads into your browser; nothing you type is uploaded. It works offline once the page has loaded.
- Completely free, no account or usage limit. It runs entirely in your browser and collects no data.
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Method & sources
How it computes
Properties and symbols follow the IUPAC-IUB nomenclature recommendations. Twenty amino acids are encoded by the standard genetic code, but twenty-two are proteinogenic: selenocysteine (Sec, U) and pyrrolysine (Pyl, O) are co-translationally inserted at recoded stop codons, which is why a table of twenty is incomplete rather than merely conventional.
What this tool implements
- One- and three-letter symbols follow IUPAC-IUB, including the ambiguity codes — B for Asx (Asp or Asn), Z for Glx, J for Leu or Ile, X for unknown — which sequence data actually contains.
- Selenocysteine and pyrrolysine are included and marked as recoded rather than omitted or silently listed among the standard twenty.
- pKa values are for the free amino acid in water at 25 C. Side-chain pKa shifts substantially inside a folded protein, so these are reference values and not predictions of behaviour in situ.
- Hydropathy values state their scale. Kyte-Doolittle and Hopp-Woods disagree in sign convention, and an unlabelled hydrophobicity number is unusable.
Sources
- IUPAC-IUB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides (Recommendations 1983). European Journal of Biochemistry 1984;138(1):9-37: https://doi.org/10.1111/j.1432-1033.1984.tb07877.x
- Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. J Mol Biol 1982;157(1):105-132: https://doi.org/10.1016/0022-2836(82)90515-0
- UniProt Consortium — the sequence database whose ambiguity codes this table must match: https://www.uniprot.org/
What can make this go out of date
- None at runtime. The table ships with the page; IUPAC-IUB symbols have been stable since 1983.
Pick up where you left off
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