Menstrual · Day 2
Today's mission
Bring her favorite chocolate home. No occasion, no comment, just chocolate.
She isn't complicated. Nobody ever explained it to you.
Hormonaut turns her cycle into one sentence a day — and one thing you can do for her today.
14 days free · cancel anytime
~13%
of the cycles studied run exactly 28 days. Normal: anywhere from 23 to 35.
Bull et al., npj Digital Medicine 2019 · 600,000+ cycles
She isn't “complicated”.
Her body runs a four-phase program.
Nobody ever explained it to you.
Energy, closeness, patience, sleep — a lot of it follows a rhythm. Know the rhythm and you understand instead of guessing. Hormonaut catches you up: five minutes instead of five semesters.
The app
One sentence a day. No more.
Where she likely is in her cycle, what that can mean today, what to pay attention to. Always a probability, never a claim. The more you observe, the sharper it gets.
Talking to her beats any app. Talking prepared beats both.
Daily mission
One thing you can do, every day.
Small, doable, effective — matched to the phase. Streak included, excuses excluded.
Follicular · Day 9
Today's mission
Suggest a walk together after dinner. Leave the phones at home.
Luteal · Day 24
Today's mission
Do the dishes tonight. All of them. Yes, the pan counts.
Science
No myths. Receipts.
- 102 studies
No robust effect of the cycle on cognitive performance. Anyone saying “she can't think straight right now” is wrong.
PLOS One 2025 · meta-analysis, 3,943 participants
- ~14 days
The luteal phase is the stable constant — the follicular phase is what varies. That's why Hormonaut estimates ovulation as cycle length minus 14.
Reproductive-medicine standard
- Both
Partners who understand PMS behave more supportively — satisfaction rises for both, and symptoms can decrease.
OAText · partner-education studies
Ten questions of cycle science, every one with a source. Free, forever.
Take the quizWhat else is inside
More tools, no noise.
- Cycle ring & daily brief
- Phase, cycle day, energy tendency, do's & don'ts — at a glance.
- Calendar with honest uncertainty
- Forecasts with a ± window instead of fake precision. The more you log, the sharper it gets.
- Phase guides
- Including “what not to say”. Learned the hard way, so you don't have to.
- Timing advisor
- When the hard conversation should wait — and when it has a real chance.
- Date ideas per phase
- From couch setup to mini adventure. Fitting, not random.
- AI coach & partner syncPremium
- A phase-aware coach for real situations — and her real data instead of estimates, if she invites you.
Privacy
Your data. Her trust.
- 01Local-first: everything stays on your device unless you enable sync.
- 02Self-hosted in the EU — no big-tech backend.
- 03No ad trackers, no data sales, no account required.
- 04Partner sync only via her explicit invite — revocable anytime.
Pricing
Try first. Decide later.
Yearly
52% cheaper€3.33 / month
14 days free
then €39.99 / year
Monthly
€6.99 / month
14 days free
then €6.99 / month
Founding Member
€99.99 once
€99.99 once — yours forever
Limited, while we're small.
- TodayUnlock everything. €0.—
- Day 12We remind you by email.
- Day 14Only now are you charged — or not.
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FAQ
Honest questions, honest answers.
Isn't this creepy?
Fair question. Hormonaut doesn't track her — it educates you. The data you enter stays on your device. It's about understanding, not surveillance. And talking to her beats any app — Hormonaut just tells you when listening matters most.
Does my girlfriend need the app?
No. Hormonaut works entirely without her — you estimate the cycle start and the app learns from your observations. If she wants, she can later share her real data via invite (Premium). She never has to.
What happens to the data?
By default: nothing — it never leaves your device. Optional sync runs through our self-hosted EU server, tracker-free. We count a few anonymous events without a user profile to see what works — no ad trackers, no third-party cookies.
Can I cancel?
Anytime, in two clicks — in the subscription portal or via the cancellation button at the bottom of this page, no login needed.
Is this medical advice?
No. Hormonaut provides probabilities and education, not diagnoses. If severe symptoms regularly disrupt her life, encourage her to seek medical advice.
Today is a good day for the hot-water bottle.
Or for chocolate. Or for listening. Hormonaut tells you which.