About

Standard period trackers often apply a rigid 28-day model that fails for many women. This tool uses a dynamic algorithm that adjusts based on cycle history and Luteal Phase Length (LPL) - the critical time between ovulation and the next period, which is typically stable (12-14 days) even when total cycle length varies.

By inputting the start dates of the last three cycles, the system calculates the average cycle length and standard deviation to flag potential irregularities (e.g., PCOS indicators). It projects the "Fertile Window" by accounting for sperm survival rates (up to 5 days pre-ovulation) and the ovum's lifespan (12-24 hours), providing a visual calendar for conception planning or natural family planning.

Formulas

Ovulation Date Prediction:

Date_ovulation = Date_{next_period} − Luteal_Phase

Fertile Window Range:

W_fertile = [Date_ovulation − 5, Date_ovulation + 1]

Cycle Variability (Standard Deviation):

σ = √∑(x − x)²N

Reference Data

Cycle Phase	Duration (Avg)	Biological Event	Fertility Status
Menstruation	3-7 Days	Shedding of endometrium.	LOW
Follicular Phase	7-21 Days (Variable)	Follicle maturation. Estrogen rises.	RISING
Ovulation	12-24 Hours	Release of egg. LH Surge.	PEAK
Luteal Phase	14 Days (Fixed)	Progesterone dominance. PMS.	LOW
Sperm Survival	Up to 5 Days	Survival in fertile cervical mucus.	Contextual

Frequently Asked Questions

Yes. 28 days is just an average. The tool calculates your personal average based on the last 3 dates you enter. If your cycle varies by more than 4-5 days (e.g., 26 days then 32 days), the "Irregularity Flag" will alert you, as prediction accuracy decreases.

The Luteal Phase is the time from ovulation to your next period. Unlike the first half of the cycle, this phase is biologically fixed for most women (usually 14 days). Knowing this allows for much more accurate ovulation prediction than simply dividing the cycle by two.

The "Rhythm Method" or calendar-based tracking has a failure rate of up to 24% with typical use. While this tool identifies high-risk days, it should not be used as the sole method of contraception, especially if you have irregular cycles.

It means the variation between your shortest and longest cycle is significant. This can be caused by stress, travel, or hormonal conditions. When the flag is active, the predicted fertile window is widened to account for uncertainty.