About GC Content · how to use, FAQ ▾
Calculate the GC content, GC percentage, AT content and full base composition of any DNA or RNA sequence. GC content is the fraction of guanine (G) and cytosine (C) bases in a sequence; it influences primer melting temperature, PCR conditions and overall sequence stability, so it is one of the first things to check when designing an experiment. Ambiguous bases are counted separately so the percentages stay accurate.
How to use GC Content
- 1Paste a DNA or RNA sequence, or a FASTA record.
- 2Read the GC% and AT% along with per-base counts for A, C, G and T/U.
- 3Use the composition to inform primer design, PCR annealing temperatures or quality checks.
Frequently asked questions
How is GC content calculated?
GC content is the number of G and C bases divided by the total number of unambiguous A, C, G and T/U bases, expressed as a percentage: GC% = (G + C) / (A + C + G + T/U) x 100.
What does GC content mean in DNA?
GC content describes how much of a DNA sequence is made of guanine and cytosine bases. Higher GC content usually means stronger base pairing and often a higher melting temperature.
Is GC content the same as GC percentage?
Yes. GC content is usually reported as GC percentage, the percent of bases in a sequence that are G or C.
How are ambiguous bases counted?
Ambiguous bases (N and other IUPAC codes) are counted separately and excluded from the GC and AT totals so the percentages reflect only unambiguous bases.