About the GC Content Calculator

Analyze GC content, base composition, and melting temperature from any DNA/RNA sequence.

What it is

The GC Content Calculator computes the percentage of guanine and cytosine bases in a DNA or RNA sequence, along with full base composition. It accepts raw sequence text or FASTA-formatted input, auto-detects DNA vs RNA, and separately reports any ambiguous IUPAC bases (like N) rather than folding them into the GC% denominator.

Features

FASTA support

Header lines are stripped automatically; multiple sequences get per-sequence stats.

Sliding-window analysis

A configurable window/step chart reveals GC-rich or GC-poor regions.

Melting temperature

Wallace rule for short sequences, GC%-based formula for longer ones.

Validation

Ambiguous bases are counted separately; empty input is blocked.

Ready to use it?

Free, no sign-up required.

Open the GC Content Calculator