Your period tracker doesn't need an ML model. It needs statistics.

Description and use

Mori is a free Android period tracker that uses simple statistics—median of up to six recent cycles—to predict the next period date locally, preserving privacy and transparency.

Problem

Users want to predict their next menstrual cycle date, but existing apps rely on machine learning models that require cloud accounts and data upload.

Outcome

Mori provides accurate, deterministic cycle predictions without cloud dependence, enhancing privacy and reliability.

Workflow

• 1. User logs up to six recent cycle lengths in Mori.
• 2. Mori calculates the median cycle length as the central estimate.
• 3. Mori outputs a date range for the next period and a confidence label based on data length and regularity.
• 4. If data is insufficient, Mori displays "not enough data" instead of a guess.

Evidence

Cycle prediction, at its core, is: take your last N cycle lengths, compute a central estimate, add a window. A mean or median over your recent history, maybe weighted toward recent cycles. That's it.

Source

I made Mori, a free Android period tracker that keeps everything on the phone. No account, no email, no cloud by default.

Source

Take up to your 6 most recent cycles; Median cycle length as the central estimate; A date range, not a single fake-precise day; A confidence label that drops when your history is short or irregular.

Source

When there's not enough data, it says "not enough data" instead of inventing a confident guess.

Source