Codon Wheel: The Standard Genetic Code as a Radial Diagram
The same 64 mRNA codons as the codon chart, arranged as four rings you read from the center outward -- first base, second base, third base, then the amino acid.
Hover (or tap, on touch devices) any outermost wedge for the full codon and amino acid name.
How to Read a Codon Wheel
Read a codon wheel from the center outward, one ring per base:
- Innermost ring -- first base. Find the wedge for your codon's first letter (U, C, A, or G). This splits the whole wheel into 4 quarter-circles.
- Second ring -- second base. Within that quarter, find the wedge for the second letter. This splits each quarter into 4 narrower wedges (16 total around the wheel).
- Third ring -- third base. Within that wedge, find the third letter. This is the final split -- 64 wedges total, one per possible codon.
- Outermost ring -- the answer. The wedge directly outside your third-base wedge shows the amino acid's 1-letter code, or an asterisk for a stop codon. Hover it (or tap, on a touch screen) for the full name.
Worked example: reading AUG through all four rings
Read the codon AUG (the start codon) around the wheel, one ring at a time:
First base A (innermost ring) → second base U (next ring out, within the A quarter) → third base G (next ring out again) → outermost ring reads M, for Methionine. AUG is also colored differently on the outer ring because it doubles as the start codon -- the ribosome uses it to mark where translation begins.
A second example, GGC: first base G → second base G → third base C → outermost ring reads G, for Glycine -- the same answer you'd get reading row-G/column-G/right-C on the codon chart.
Common mistake
Reading the rings out of order -- for example, picking the second base before the first, or reading the outer amino-acid ring before narrowing down to a single third-base wedge. The wheel only gives one correct codon per path; always work strictly center-to-edge, one base at a time, in first-second-third order.
Keep going
- Prefer a grid you can scan by row and column instead of rings? This is the exact same standard genetic code laid out as a table in the Codon Chart
- The outer ring's colors and 1-letter codes come straight from the 20 standard amino acids' full names, classifications, and molecular weights on the Amino Acid Chart
- Once you've read an amino acid off the wheel, look up its molecular formula on the Amino Acid Chart and total its molecular weight with the Molar Mass Calculator
- Preparing a solution of a specific translated amino acid uses the same concentration math as the Molarity Calculator
Frequently Asked Questions
What is a codon wheel?
A codon wheel is a circular diagram of the standard genetic code: the same 64 codons as a codon chart, arranged as four concentric rings instead of a grid. The innermost ring is a codon's first base, the next ring out is its second base, the next is its third base, and the outermost ring is the amino acid (or Stop) that triplet codes for. It's a classic biology-classroom tool because reading center-to-edge mirrors reading a codon left-to-right, one base at a time.
How do I read a codon wheel?
Start at the center and work outward. First, find your codon's first base as a wedge in the innermost ring. Then, within that wedge, find the second base in the next ring out. Then, within that narrower wedge, find the third base in the ring after that. The outermost wedge directly above your third-base wedge shows the resulting amino acid's 1-letter code, or an asterisk (*) for a stop codon.
Is a codon wheel the same information as a codon chart?
Yes -- a codon wheel and a codon chart (grid) encode the identical standard genetic code, just laid out differently. Some people find the grid faster for looking up one specific codon; others find the wheel's center-outward reading order more intuitive, especially when first learning translation, since it echoes reading the codon's three letters in order. Neither is more "correct" -- pick whichever layout clicks for you, or use both.
Why does the wheel use 1-letter amino acid codes instead of 3-letter codes?
Space. The outermost ring has 64 separate wedges around a single circle, so a 1-letter code (like M for methionine) fits far more legibly than a 3-letter code (Met) would at that width. Hovering any outer wedge shows the full amino acid name, its 3-letter code, and its 1-letter code together.
What do the colors on the outer ring mean?
The outermost ring is color-coded by the same 5-group side-chain classification used on this site's Amino Acid Chart -- nonpolar, aromatic, polar, acidic, and basic -- so you can see at a glance which amino acids are chemically similar, plus a distinct color each for the start codon (AUG) and the three stop codons.
Why do some outer wedges cover more of the circle than others?
They don't -- every wedge in every ring is exactly the same angular width within its ring, because there are always exactly 4 choices at each base position. What varies is how many separate wedges end up labeled with the same amino acid: leucine, serine, and arginine each get 6 separate outer wedges (their 6 codons), while methionine and tryptophan each get exactly 1, because the genetic code assigns them only a single codon.
Source: NCBI Genetic Codes -- The Standard Code (translation table 1) (https://www.ncbi.nlm.nih.gov/Taxonomy/Utils/wprintgc.cgi), fetched 2026-09-25. Same dataset as the codon chart, reshaped into ring order -- see that page for the full grid and codon-level FAQ.
Related Calculators
- Molarity Calculator — Solutions & Concentration
- Dilution Calculator — Solutions & Concentration
- Molality Calculator — Solutions & Concentration
- Molar Mass Calculator — Atomic & Molecular