GC Content Calculator
Calculate the GC content percentage of any DNA or RNA sequence.
Shows nucleotide composition, complementary strand, and molecular weight estimate.
What Is GC Content? GC content is the percentage of bases in a DNA or RNA sequence that are either guanine (G) or cytosine (C). It is calculated as: GC% = (G + C) / (A + T + G + C) x 100 for DNA, or (G + C) / (A + U + G + C) x 100 for RNA.
Why GC Content Matters G-C base pairs form three hydrogen bonds (stronger) while A-T pairs form only two. Higher GC content means higher melting temperature and greater thermal stability. Organisms in high-temperature environments (thermophiles) tend to have higher GC content in their genomes.
Typical GC Content Values Human genome: ~41% GC. E. coli: ~50.8% GC. Mycobacterium tuberculosis: ~65% GC. Plasmodium falciparum (malaria): ~19% GC (extremely AT-rich). Thermus aquaticus (source of Taq polymerase, used in PCR): ~69% GC.
Applications PCR primer design: primers should ideally have 40-60% GC content. Genome classification: GC content is used to classify and compare organisms. Codon usage: organisms with different GC contents show different codon preferences. Horizontal gene transfer detection: genes with unusual GC content may have been acquired from other species.
Chargaff’s Rules In double-stranded DNA, the amount of A equals T, and G equals C (Erwin Chargaff, 1950). However, in single-stranded DNA, RNA, or specific genes, these ratios can vary. GC content can be measured for single strands, individual genes, or entire genomes.