METHODOLOGYHow Plumm predicts your cycle so precisely.
Our algorithm doesn't guess. It learns from your real cycles, on clinical foundations. We explain it all, simply.
Day-accurate after 3 cycles
The more you log, the more the prediction sharpens. The algorithm learns from YOU.
8 clinical signals
Mucus, ovulation pain, libido, spotting… each weighted by the clinical literature.
Sources: Hilgers, Billings, ACOG
We cite our references — and ship them in our code.
The starting point: Ogino, only better
Most apps predict from an « average » 28-day cycle with ovulation on day 14. That's the Ogino method, a hundred years old — right for no one, because nobody has a perfectly average cycle.
Plumm starts there, then sharpens it with two things: your real cycle lengths, and the signals you log.
Your cycles, not an average
The moment you log your period, Plumm remembers your real cycles. With each new one, we recompute your average — giving more weight to recent cycles (your last 5 count more than those from 6 months ago).
Outlier cycles (under 15 or over 60 days) are filtered out. The result: your « average » cycle is yours. Not the population's.
8 clinical signals, each weighted
Other apps stop here. Plumm goes further: log physiological signals and we adjust your prediction in real time.
Each signal carries a weight drawn from clinical research: • Egg-white mucus (0.8) — the most reliable for spotting ovulation (Hilgers, Billings) • Watery mucus (0.6) — fertile window • Dry mucus after the peak (0.85) — ovulation has passed • Ovulation pain (0.8) • Libido peak (0.4) • Spotting (0.85) — cycle start • Premenstrual pain (0.5) • Premenstrual mood (0.4)
Yesterday counts more than last week
A signal has a shelf life. Yesterday's counts at 80 % of its weight, the day before at 64 %, and so on. Past 10 days, we ignore it.
Like a gynecologist reading your most recent signs first.
The 70/30 blend
The algorithm never blindly follows a single signal. The final prediction is 70 % your recent signals + 30 % your average.
This anchor prevents drift: one misread signal can't pull you far from your reality.
And if there's a doubt?
If Plumm sees signals that contradict each other (an ovulation cue AND a period cue within 3 days), it switches to cautious mode: baseline prediction + low confidence. And it tells you why.
A « not sure » beats a false certainty.
The limit, because we have to say it
Plumm is a tracking tool, not a medical device. Even with the best algorithm, predicting ovulation 100 % of the time is impossible — the body isn't a clock.
For contraception, use a real method. To plan a pregnancy, get proper support. With a long delay, abnormal pain or unusual bleeding: see a professional. We walk with you, we don't replace a doctor.
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