๐งฌGC Content Calculator
Paste a DNA/RNA sequence or FASTA file to get GC%, base composition, sliding-window analysis, and Tm.
Free GC Content Calculator
Our free GC content calculator analyzes any DNA or RNA sequence instantly. Paste in raw text or a full FASTA file, and get GC%, AT/AU%, total length, and exact base counts in one view โ no manual counting required.
For deeper analysis, use the sliding-window mode to see how GC content varies across the length of your sequence, plotted as a simple chart โ handy for spotting GC-rich or GC-poor regions. The tool also estimates melting temperature using the Wallace rule for short primers or a GC%-based formula for longer sequences, with the formula shown so you know exactly how it was calculated.
Multi-sequence FASTA files are supported too, with per-sequence stats summarized in a table. Free, fast, and fully private โ your sequence never leaves your browser.