Period & Ovulation Calculator
Track menstrual cycles and predict fertile windows with a privacy-first, 3-month visual calendar. No login required.
About
Understanding the menstrual cycle is fundamental for both conception planning and general health monitoring. The cycle consists of the follicular phase, ovulation, and the luteal phase. Identifying the fertile window - the days surrounding ovulation - is critical for those trying to conceive, as sperm can survive for up to 5 days, while the egg is viable for only 24 hours.
This calculator employs the standard calendar method to project future dates. Unlike mobile apps that harvest sensitive health data, this web tool operates entirely client-side. It features a strict Privacy Mode to protect your screen from prying eyes in public spaces.
Formulas
If D is the first day of the last period and L is the average cycle length:
Note: The luteal phase is generally consistent at 14 days, which is why ovulation is calculated backwards from the next projected period.
Reference Data
| Phase | Approx. Days | Hormonal Activity | Symptoms |
|---|---|---|---|
| Menstruation | 1 - 5 | Estrogen/Progesterone Drop | Bleeding, Cramps, Fatigue |
| Follicular Phase | 6 - 13 | FSH Rise, Estrogen Rise | Higher Energy, Clearer Skin |
| Ovulation | 14 | LH Surge | Egg Release, High Libido, Mittelschmerz |
| Luteal Phase | 15 - 28 | Progesterone Rise | PMS, Bloating, Mood Changes |