Ovulation Calculator
Estimate your ovulation date, fertile window and most fertile days from your cycle.
Ovulation ≈ —
Your cycle phases
Relative chance of conception by day
Next three cycles
Personalised guidance
How to use the Ovulation Calculator
Step 1 — Enter your dates
- Add the requested dates and details.
Step 2 — See your results
- Key dates and a visual timeline update instantly.
Step 3 — Explore
- Review the breakdown, schedule and guidance.
Step 4 — Export
- Download a PDF to share with your provider.
Frequently asked questions
In a regular cycle, ovulation happens about 14 days before your next period — so on a 28-day cycle, around day 14. The tool calculates this from your cycle length, since the luteal phase is the more constant part.
The roughly six days ending on ovulation day: the five days before (sperm can survive that long) plus ovulation day itself. The two to three days just before ovulation are the most fertile.
No. This is not a reliable contraceptive method. Ovulation timing varies between cycles even when periods seem regular, so for preventing pregnancy use a proper contraceptive and speak to a healthcare professional.
Calendar predictions become much less reliable with irregular cycles. Ovulation predictor kits or basal body temperature tracking are more accurate, and a doctor can help if cycles are very unpredictable.
Having intercourse every one to two days through the fertile window covers the most fertile days. If you have been trying for over a year — or six months if you are over 35 — see a doctor. This tool gives general information for education, not medical advice; always follow your midwife, doctor or other qualified healthcare professional.
About the Ovulation Calculator
This tool estimates the days you are most likely to conceive — your ovulation date and fertile window — from the first day of your last period and your usual cycle length. It also shows your relative chance of conception by day, maps your cycle into its phases, and projects the next few cycles so you can plan ahead.
How it estimates ovulation
It works from a reliable piece of reproductive biology: the luteal phase (from ovulation to your next period) is fairly constant at about 14 days, while the first half of the cycle varies. So the tool counts back roughly 14 days from your predicted next period to place ovulation, then marks the fertile window as the five days before plus ovulation day — because sperm can survive several days in the body while the egg lives only about 24 hours. That is also why conception is most likely in the two to three days before ovulation, not after, which the day-by-day chart makes clear.
Plan with the cycle view
The cycle phase bar shows where you are today — menstrual, follicular, fertile or luteal — and the multi-cycle table projects upcoming periods, fertile windows and ovulation dates so you can plan around them. Watching for natural signs (clear, stretchy cervical mucus; a small temperature rise after ovulation) adds confidence to the estimate.
Important limits
This is not a method of contraception. Ovulation shifts from cycle to cycle, so calendar timing is far too uncertain to prevent pregnancy — use a reliable contraceptive for that. For conceiving, predictor kits or temperature tracking beat the calendar, especially with irregular cycles. This tool gives general information for education, not medical advice; always follow your midwife, doctor or other qualified healthcare professional. When you conceive, the Pregnancy Due Date Calculator takes over from here.