How to Calculate Menstrual Cycle
What is Menstrual Cycle?
A menstrual cycle calculator tracks the timing of periods, ovulation, and fertile windows based on cycle length and period duration. The average cycle is 28 days (range 21–35 days), with ovulation typically occurring 14 days before the next expected period.
Formula
Step-by-Step Guide
- 1Next period = Last period start + Cycle length
- 2Ovulation = Next period − 14 days
- 3Fertile window = Ovulation day ± 5 days (sperm viable 5 days; egg viable 12–24 hours)
- 4Luteal phase (ovulation to next period) is relatively fixed at ~14 days
Worked Examples
Frequently Asked Questions
What is Menstrual Cycle?
A menstrual cycle calculator tracks the timing of periods, ovulation, and fertile windows based on cycle length and period duration. The average cycle is 28 days (range 21–35 days), with ovulation typically occurring 14 days before the next expected period
How accurate is the Menstrual Cycle calculator?
The calculator uses the standard published formula for menstrual cycle. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Menstrual Cycle calculator use?
This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Menstrual Cycle calculator use?
The core formula is: Next period = Last period start + Cycle length. Each step in the calculation is shown so you can verify the result manually.
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