CpG Island Finder

DNA sequence

Window sizeMinimum observed/expected CpGMinimum GC %

Output

How to find CpG islands

Paste a DNA sequence, as plain text or FASTA.
Keep the usual thresholds (a 200-base window, at least 50% GC and an observed/expected CpG of at least 0.6) or change them.
Windows that pass are merged into regions, listed with their length, GC content and observed/expected CpG.

Frequently asked questions

How is observed/expected CpG worked out?

The number of CG dinucleotides times the window length, divided by the number of C times the number of G.

Is my sequence uploaded?

No. Everything runs in your browser, so your sequences never leave your device.

Embed this tool on your site

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Guides

DNA and Protein Sequence Statistics Explained How to Find CpG Islands in a DNA Sequence How to Calculate GC Content