Estimate your fertile window based on your cycle. For general awareness only — not a contraception tool.
📋 Source: Ovulation prediction based on typical menstrual cycle length. Results are estimates only — individual variation is significant. Not a contraceptive tool. Consult your GP or gynaecologist for personalised advice on fertility or contraception. Information is general in nature. Always consult a qualified healthcare professional for advice specific to your situation.
⚠️ Not a contraception tool. Ovulation timing varies significantly between cycles and is affected by illness, stress, and many other factors. This calculator gives a rough estimate only. For contraception advice, speak with your GP.
Estimated dates — current cycle
PeriodFertile windowEstimated ovulation
Period start
Fertile window starts
Estimated ovulation day
Fertile window ends
Next period (estimated)
Estimated due date (if conceived)
These dates are estimates based on average cycle physiology. Actual ovulation can vary by several days even in regular cycles. This tool assumes ovulation occurs 14 days before the next period (the luteal phase is approximately constant at 14 days; the follicular phase varies). Women with irregular cycles, PCOS, thyroid conditions, or those who are breastfeeding should discuss cycle tracking with their GP or gynaecologist.
This calculator cannot be used as a method of contraception. For contraception advice, speak with your GP.
Sources
Wilcox AJ, Dunson D, Baird DD. The timing of the "fertile window" in the menstrual cycle: day specific estimates from a prospective study. BMJ. 2000;321:1259–1262. doi:10.1136/bmj.321.7271.1259
Direkvand-Moghadam A, et al. Epidemiology of Premenstrual Syndrome — A Systematic Review and Meta-Analysis Study. Journal of Clinical and Diagnostic Research. 2014.
Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG). Menstruation and fertility. ranzcog.edu.au