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Flo vs Periodical: catalog facts
Flo	Periodical
Best for: People tracking their menstrual cycle, ovulation or pregnancy on a phone	Best for: Android users who want a private, open-source period calendar
Free + paid options Free to download, with a paid premium subscription.	Free Free and open source under the GPL-3.0-or-later licence.
Android, iOS	Android
Tracks periods, ovulation and pregnancy in one app Symptom logging alongside cycle dates	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
Proprietary service that handles sensitive health data Some features require a paid subscription	Calendar method is not reliable for contraception Simple feature set compared with commercial cycle trackers
Downloadable app, Hosted service	Downloadable app
Not open source	Open source
License not stated	License: GPL-3.0-or-later
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Sources for Flo flo.health play.google.com/store/apps/details apps.apple.com/us/app/flo-cycle-period-tracker/id1038369065 Catalog checked September 23, 2026	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

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