Period Calculator
Predict your next period, identify your most fertile days, and track your ovulation cycle with precision.
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Understanding Your Cycle
The menstrual cycle is broken into distinct phases that dictate when you bleed and when you are most fertile.
Menstruation (Your Period)
Day 1 of your cycle is the first day of full bleeding. This phase usually lasts between 3 to 7 days as the uterine lining sheds.
The Fertile Window
This window opens about 5 days before ovulation and closes 1-2 days after. Because sperm can survive in the body for days, having intercourse before the egg is released increases the chance of pregnancy.
The Luteal Phase
This occurs strictly after ovulation and before the next period starts. Unlike the variable first half of the cycle, the luteal phase is consistently about 14 days long for most healthy adults.
Frequently Asked Questions
How is my next period date calculated?
We take the first day of your last period and add your average cycle length to it. For example, if your last period started on January 1st and your cycle is 28 days long, your next period is predicted to start on January 29th.
How do you calculate ovulation day?
Ovulation typically occurs about 14 days before the start of your NEXT period, regardless of how long your cycle overall is. This is because the second half of the cycle (the luteal phase) is relatively constant for most women at 14 days. We simply subtract 14 days from your predicted next period start date.
What is the "Fertile Window"?
The fertile window comprises the 5 days leading up to ovulation, plus the day of ovulation itself, and sometimes the day after. Sperm can survive inside the female reproductive tract for up to 5 days, while an egg only survives for 12-24 hours after release. Having intercourse during this window maximizes the chances of conception.
Can my cycle length change?
Yes, it is completely normal for cycle lengths to vary slightly from month to month due to factors like stress, diet, travel, illness, or hormonal changes. A "regular" cycle is generally considered to be anywhere between 21 and 35 days.
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