N bases are included in the total length but counted as neither G/C nor A/T, so a sequence with Ns can read lower than the called bases alone suggest.

Is it case sensitive?

No — input is read case-insensitively.

GC content calculator

Calculate the percentage of G and C bases in a DNA sequence, with base counts. Handy for primer design and assessing sequence composition.

How it works

Formula

GC% = (count of G + count of C) ÷ total length × 100

Worked example

GGCCATAT has 4 G/C bases out of 8: 4 ÷ 8 × 100 = 50%.

When to use it

To gauge primer or probe stability, anticipate melting behaviour, or flag GC-rich and GC-poor regions that can be hard to amplify or sequence.

Sensible defaults

The default GGCCATAT is 50% GC — a balanced example.

FAQ

Do N bases count?: N bases are included in the total length but counted as neither G/C nor A/T, so a sequence with Ns can read lower than the called bases alone suggest.
Is it case sensitive?: No — input is read case-insensitively.