Know Her vs
Mayday

"Stock supplies, be patient, offer support" — that's the entire app. Understanding her deserves more than a fridge magnet.

★  Actual understanding, not a canned tip
Know Her period tracker app — home screen widget showing her cycle phase

Three suggestions on a three-day timer isn't understanding her — it's a countdown with a script attached.

Mayday keeps things extremely simple: enter a few dates, and three days before her predicted period you get one of three canned lines — "Stock supplies," "Be patient," "Offer support." That's the entire app, every cycle, whether or not it actually fits what's going on with her. Know Her covers what those three lines can't: her current phase, mood, and energy every single day, not just a countdown before her period — and predictions self-calibrate as you confirm more cycles instead of repeating the same three suggestions forever.

What each app actually gives you

One is a heads-up. The other is a daily picture.

Mayday

  • A 3-day alert before her predicted period — that's the core feature.
  • Three canned suggestions — "Stock supplies," "Be patient," "Offer support."
  • No sign it self-calibrates — predictions appear fixed once you enter her dates.

The same three lines, every cycle, whether they fit or not. That's not support — that's a script.

Know Her

  • The date her last period started. Then a full daily dashboard — mood, energy, guidance.

Something to check every day, not just before her period — and it improves the longer you use it.

Feature comparison

Know Her vs Mayday, side by side.

Know Her Mayday
Built for male partners ✓ Purpose-built ✓ Purpose-built
She needs no app or account ✓ Yes ✓ Yes
You need an account to log in ✓ No ✓ No — "no sign-up required" per its listing
Daily mood and energy dashboard ✓ Yes, every day ✗ Only a 3-day pre-period alert
Predictions self-calibrate ✓ Yes — learns her cycle ✗ No sign of self-calibration
100% offline ✓ Yes ✓ Yes, per its listing
Home screen widget ✓ Yes ✗ Not listed
Multiple languages ✓ 6 languages ✗ English only
Private notes on the calendar ✓ Yes — offline, only yours ✗ No
Your price $2.99/mo — 14-day free trial Free, Gold at $7/mo or $42/yr

Design intent matters

What the app was built to solve changes everything about how it works.

Know Her

  • ✓ Daily dashboard: mood, energy, guidance
  • ✓ Self-calibrates to her specific cycle over time
  • ✓ Widget: one-tap phase check from the home screen
  • ✓ Private notes and reminders on the calendar
  • ✓ 6 languages, matches your device automatically
  • ✓ Face ID lock for extra privacy

Mayday

  • ✓ Extremely simple — a 3-day alert and 3 suggestions
  • ✗ Nothing day-to-day beyond the pre-period warning
  • ✗ No indication predictions improve over time
  • ✗ No home screen widget found
  • ✗ English only

Price comparison

What it actually costs you.

Know Her Free to download — full access for 14 days

Then $19.99/year (or $2.99/month). Daily dashboard, self-calibration, widget, Face ID lock, private notes.

Mayday Free Gold tier: $7/mo or $42/yr

Free for the basics; its own Gold tier costs more per year than Know Her's full subscription.

Know Her costs less than Mayday's own Gold tier — and gives you a daily dashboard, not just a warning.

Common questions

About choosing between Know Her and Mayday.

A simple three-day alert before her predicted period, with three canned suggestions: "Stock supplies," "Be patient," "Offer support." It's built for men who want the bare minimum and nothing more. Know Her gives a daily dashboard — her current phase, mood, energy, and practical guidance every day, not just a heads-up before her period.
There's no indication that it does. Mayday appears to work off the dates you enter once, without adjusting as her actual cycle plays out. Know Her self-calibrates — every confirmed period makes its predictions more accurate to her specific rhythm.
Yes, Mayday's base app is free, with an optional Gold tier at $7/month or $42/year for additional features. Know Her is free to download, with a 14-day trial that includes full access, then just $2.99/month or $19.99/year — less than Mayday's own premium tier, and it self-calibrates by default.
Yes. Know Her stores everything on your device — no account, no cloud, no sync. All data stays on your phone. You can lock it with Face ID or biometrics for extra privacy.
No. Know Her works entirely from information you enter yourself — no account for her, nothing to install, nothing to share. You just need the date her last period started. She doesn't even need to know you're using it.
Yes. Everything stays on your phone — no account, no cloud, no sync, nothing to leak. You can lock the app with Face ID or biometrics for extra privacy on top of that.
You get 14 days of full access, completely free. After that, Know Her runs on a simple subscription — monthly or annual. Cancel anytime directly in your App Store settings.
No. Know Her is designed to help you understand and plan around her cycle — it's not a medical device, diagnostic tool, or method of contraception. For health decisions, always consult a healthcare professional.

More comparisons

See how Know Her stacks up against other apps.

Know Her vs Flo for Partners Know Her vs Clue Connect Know Her vs Stardust Know Her vs Selin Know Her vs Maya Know Her vs Yuni Know Her vs Phases Know Her vs GF Tracker Know Her vs DuoSync

Available on
iOS & Android.

Free for 14 days.

No commitment. Cancel anytime.

Download on the App Store
Get it on Google Play