Cycle Details
Click any day on the calendar below or select a date preset to set the first day of your last period.
No Period Date Selected
Select the first day of your last period on the calendar above, type your date into the input field, or choose a quick date preset to calculate your next period and fertility window.
Frequently Asked Questions
How is my next period calculated?
Your next period is predicted by adding your average cycle length to the first day of your last period. For example, with a 28-day cycle starting on 1 March, the next period is due around 29 March.
When am I most fertile?
You are most fertile in the 5 days before ovulation and on ovulation day itself. The chance of pregnancy is highest in the 2 days before ovulation and on the day of ovulation.
When do I ovulate?
Ovulation usually happens about 14 days before your next period. That is day 14 only in a 28-day cycle; in a 32-day cycle it is closer to day 18.
What is a normal menstrual cycle length?
For adults, a cycle of 21 to 35 days is normal, with bleeding for 2 to 7 days. In the first few years after periods start, cycles of up to 45 days can be normal.
Does this work if my periods are irregular?
Predictions are less reliable when cycle length changes from month to month. Ovulation test kits or tracking cervical mucus can help. See a doctor if your cycles are often shorter than 21 days, longer than 35 days, or very unpredictable.
Can I use a period calculator as birth control?
No. Calendar predictions are estimates and ovulation can shift with stress, illness or travel. Use a reliable contraceptive method if you want to avoid pregnancy.
Can I get pregnant on my period?
It is unlikely but possible, especially with short cycles, because sperm can survive up to 5 days and ovulation may happen soon after bleeding ends.
Clinical note: Menstrual dates and fertility windows are estimations based on regular cycle patterns. Ovulation timing can fluctuate due to stress, illness, sleep, or hormonal changes. This calendar is an educational tracking aid and should not be relied upon as a primary contraceptive method.