Calculates the percentage of a DNA or RNA sequence made up of guanine (G) and cytosine (C) bases.
How it works
Every G and C base in the sequence is counted, then divided by the total sequence length and converted to a percentage.
What this does not include
This does not include melting temperature prediction directly — GC content is one input to those calculations, but this calculator specifically reports the percentage itself.
How to use this calculator
- Enter a DNA or RNA sequence using only the letters A, T, G, C (or U for RNA).
A worked example
The sequence ATGCGCTA (8 bases): 4 of the 8 bases are G or C, giving 50% GC content.
The sequence AAAATTTT: no G or C bases at all → 0% GC content.
What the variables mean
| Variable | Meaning |
|---|---|
| Sequence | A DNA sequence, using the letters A, T, G, C |
| GC content | Percentage of bases that are G or C |
Edge cases worth knowing
GC content reflects genomic stability — G-C base pairs form three hydrogen bonds versus two for A-T, so higher GC content generally means a more thermally stable DNA strand.
A sequence containing characters other than A, T, G, C is invalid — the calculator declines to show a result rather than silently ignoring unrecognized letters.
Frequently asked questions
Why does GC content matter?
A G-C base pair forms three hydrogen bonds versus two for an A-T pair, so higher GC content generally means a more thermally stable DNA strand with a higher melting temperature.
Does GC content vary between organisms?
Yes — different species and even different regions of the same genome can have very different GC content, which is sometimes used in genome comparison and identification.
Can I use this for RNA sequences?
Yes — enter U in place of T for RNA; the G and C count works the same way regardless.
