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Questions and answers

• How does Mori calculate ovulation estimates when my cycle history is short or highly irregular, and how does it show how uncertain those estimates are?

  Asked by SaaS Browser · November 2, 2026

  Answered by Alfred Chaos from Mori · November 3, 2026

  Sure, happy to explain.
  Mori estimates ovulation by counting back from your predicted next period: cycle length minus about 14 days for the luteal phase. The fertile window is the 5 days before that through the ovulation day. It only uses your own logged history — nothing leaves the device, and there's no remote model involved.
  When you've only logged one or two cycles, it doesn't lean on that data too hard. It pulls the projection toward your default setting so one unusual month doesn't throw the estimate off (the pull is stronger with one cycle than two). And if the projected cycle comes out under 15 days, it doesn't show an ovulation estimate at all. Showing nothing felt better than showing a made-up number.
  For irregular cycles the main thing is you never get a single date. The next period always comes as a range, and the thinner or messier your history is, the wider it gets. Early on it's a fixed ±5 days or
  so. Once there's more history it backtests its own past predictions against what actually happened and sizes the range to cover about 80% of the misses.
  On screen it's all labeled for what it is: ovulation shows as "approx.", the calendar says "estimated", there's a low/medium/high confidence indicator, and when your history is thin it tells you roughly how many more periods to log before it tightens up.
  So it works best the longer you use it, and the range is where it's being honest about what it doesn't know yet.

• No Ads
  Mori has no pop-ups, banners, or splash screens to interrupt you.
• Data Export
  You can export your records as JSON, CSV, or a simple summary anytime.
• Data Transfer
  You can move your data to a new phone easily with optional sync.
• Free Features
  Logging, history, estimates, stats, and export are all free and will stay free.
• Privacy First
  Mori keeps your data private and does not ask unnecessary questions like pregnancy tracking.
• Works Offline
  You can use Mori without internet, even when your phone is offline.
• Simple Interface
  Mori opens directly to your calendar with no ads or extra steps.
• No Account Needed
  You do not need to create an account to use Mori.
• Accurate Estimates
  It makes period and ovulation estimates based on your own history.
• Adjusts for Variations
  If your cycle days change, Mori adjusts its predictions automatically.