How ovulation is estimated
Ovulation usually happens about 14 days before your next period. With a 28-day cycle that is around day 14; with a 32-day cycle, around day 18. Sperm can live up to 5 days, so the fertile window starts 5 days before ovulation.
Signs of ovulation
- Clear, stretchy cervical mucus, like raw egg white
- A small rise in morning body temperature after ovulation
- Mild one-sided lower belly pain for some women
- A positive result on an ovulation (LH) test kit
Frequently asked questions
Can I get pregnant outside the fertile window?
It is unlikely but possible, especially if your cycles vary. Ovulation can shift from month to month.
Can I use this as birth control?
No. Calendar estimates are not reliable enough to prevent pregnancy.
When should we see a doctor?
If you are under 35 and have tried for 12 months, or 35 and over and have tried for 6 months, see a fertility specialist.
Sources
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. New England Journal of Medicine, 1995.
- American College of Obstetricians and Gynecologists. Methods for estimating the due date (Committee Opinion 700), 2017. Link
Medical disclaimer: This calculator gives estimates for general information only. It is not a diagnosis or a substitute for advice from a doctor or registered dietitian. Please consult a healthcare professional before making changes to your diet, exercise or medicines, especially if you are pregnant, have a medical condition or take regular medication.
Last updated: 20 October 2026. Read our editorial policy.
