Ovulation Calculator
What this tracker does
The Menstrual / Ovulation Tracker estimates your upcoming period, ovulation day, and fertile window based on your average cycle length. It helps you better understand your cycle so you can plan around symptoms, fertility, and self-care.
Cycles can change from month to month. The dates shown are estimates, not guarantees.
How the tracker works
- Choose the first day of your last period.
- Enter your average cycle length in days (from one period start to the next).
- Enter your typical period length (how many days you usually bleed).
- Click Calculate to see your estimated next period, ovulation day, and fertile window.
- Use Copy or Share buttons to save or send your results.
What the inputs mean
- First day of last period: the first day you had normal flow (not just light spotting).
- Average cycle length: days from the start of one period to the start of the next (often 21–35 days).
- Period length: how many days you usually bleed each cycle.
If your cycles vary, use a recent average from several months rather than a single unusual cycle.
How the dates are estimated
- Next period: counted forward from the last period using your average cycle length.
- Period end: next period start plus your usual period length.
- Ovulation day: estimated about 14 days before your next period.
- Fertile window: usually the 5 days before ovulation and about 1 day after.
These are patterns based on a “typical” cycle; your body may behave differently each month.
Understanding your cycle phases
- Menstrual phase: bleeding days. Hormone levels are low; many people feel more tired.
- Follicular phase: from period end to ovulation. Estrogen rises; energy and mood often improve.
- Ovulation: release of an egg. Fertility is highest around this time.
- Luteal phase: from after ovulation to the next period. PMS symptoms can appear for some people.
Tracking patterns over several months can help you spot what is “normal” for you.
Helpful tips
- Use the same time zone and calendar format each time you track.
- Write down symptoms like cramps, mood, or energy to see patterns.
- Update your inputs if your cycle length changes for several months.
- Use the tracker as a guide, not as the only source of fertility information.
Important reminders
- Stress, illness, travel, and medications can shift your cycle.
- Irregular or very long cycles can make predictions less accurate.
- This tool is not reliable as a contraceptive method.
- If periods are very painful, very heavy, or frequently late/missed, talk to a healthcare professional.
Frequently asked questions
My cycle length changes. Will this still work?
The tracker uses the average cycle length you enter, so it can still be useful. However, more irregular cycles mean wider possible ranges around the predicted dates.
Can I use this tracker to avoid pregnancy?
No. This is an educational tool and should not be used as your only method of contraception. Always speak with a healthcare provider about safe and effective birth control.
What if I do not remember my exact last period date?
Use your best estimate and update the tracker once you are sure of your next period’s start date. The more accurate the input, the more useful the predictions.
When should I see a doctor about my cycle?
If your period suddenly stops, becomes very heavy, is extremely painful, or if cycles are consistently shorter than 21 days or longer than 35 days, it is a good idea to seek medical advice.
Important note
This tracker is for information and education only. It does not diagnose conditions or replace professional medical advice. If you have concerns about your cycle, fertility, or symptoms, please consult a healthcare provider.