Enter the first day of your last period and your usual cycle length. The calculator estimates when you ovulate, your fertile days, your next period and the earliest day for a pregnancy test.
This calculator gives a general estimate for adults and is not medical advice. Talk to a doctor or a registered dietitian before making health decisions.
How it works
Ovulation usually happens about 14 days before the next period starts, so with a 28-day cycle it falls around day 14 and with a 32-day cycle around day 18.
The fertile window is the five days before ovulation plus the day after it, because sperm can survive several days. The two or three days just before ovulation are the most fertile.
Cycles vary from month to month, so treat these dates as estimates. Ovulation tests, basal body temperature and cervical mucus changes give a more precise picture.
Common questions
Can I use this as contraception?
No. Calendar estimates are not reliable enough to prevent pregnancy, especially with irregular cycles.
What if my cycles are irregular?
Use your average cycle length, and consider ovulation test kits. Speak to a doctor if cycles are very irregular or you have been trying to conceive for over a year (six months if over 35).