GC Content Calculator
By Santaji GadepatilinUpdated October 27, 2026
bases
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Type in any field to change it. Press × on a value to calculate that field instead.
How to use this calculator
Enter the counts of G, C, A and T (use T for U in RNA). The total length and GC content are calculated.
Formula
GC% = (G + C) ÷ (A + T + G + C) × 100
Example
G = 120, C = 110, A = 140, T = 130 → total 500 bases → GC = 46%
Frequently asked questions
What is GC content?
The percentage of bases in a sequence that are guanine (G) or cytosine (C).
Why does GC content matter?
G–C pairs have three hydrogen bonds versus two for A–T, so GC-rich DNA is more stable and melts at a higher temperature.
What is a typical GC content?
About 40–42% for the human genome; bacteria range from under 25% to over 70%.