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Periodical vs Natural Cycles: catalog facts
Periodical	Natural Cycles
Best for: Android users who want a private, open-source period calendar	Best for: People looking for hormone-free birth control or fertility tracking
Free Free and open source under the GPL-3.0-or-later licence.	Paid Subscription service; prices are not listed on the homepage.
Android	Android, iOS
Calculates fertile days and tracks symptoms and notes Backup to a single compressed file on local storage All 4 strengths for Periodical Calculates fertile days and tracks symptoms and notes Backup to a single compressed file on local storage Available from F-Droid, Google Play or as an APK Translated through a community Crowdin project	FDA-cleared as a birth control app Covers contraception, pregnancy planning, postpartum and perimenopause All 3 strengths for Natural Cycles FDA-cleared as a birth control app Covers contraception, pregnancy planning, postpartum and perimenopause Works with an overnight band and other compatible devices
Calendar method is not reliable for contraception Simple feature set compared with commercial cycle trackers	Less effective than an IUD, with 93% typical-use effectiveness Requires regular temperature or biomarker measurements All 3 limitations for Natural Cycles Less effective than an IUD, with 93% typical-use effectiveness Requires regular temperature or biomarker measurements Pricing not listed on the homepage
Downloadable app	Downloadable app
Open source	Not open source
License: GPL-3.0-or-later	License not stated
Not stated if an account is needed	Account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Sources for Periodical arnowelzel.de/projekte/periodical f-droid.org/packages/de.arnowelzel.android.periodical Catalog checked October 2, 2026	Official website Full listing and sources Sources for Natural Cycles naturalcycles.com play.google.com/store/apps/details apps.apple.com/us/app/natural-cycles-fertility-app/id765535… Catalog checked September 24, 2026

“Not stated” means we have not confirmed it. Features can vary by device and plan.