How we predict ovulation
The second half of the menstrual cycle – the luteal phase, from ovulation to your next period – is fairly constant at around 12–14 days. The first half (the follicular phase) is what varies. So instead of counting forward from your period, the calculator counts backwards from your next expected period:
Your fertile window is the five days before ovulation plus the day of ovulation. The two days just before ovulation carry the highest chance of pregnancy.
Signs you are ovulating
- Cervical mucus changes: it becomes clear, slippery and stretchy – like raw egg white – in the days before ovulation.
- Mild one-sided pelvic pain (mittelschmerz) for a few hours.
- Increased libido and sometimes breast tenderness.
- A small rise in basal body temperature (about 0.2–0.5 °C) that stays up after ovulation.
Ways to confirm ovulation
| Method | What it tells you | Notes |
|---|---|---|
| Ovulation (LH) test strips | LH surge 24–36 h before ovulation | Widely available at Indian pharmacies; start testing a few days before your predicted date |
| Basal body temperature | Confirms ovulation after it happens | Take temperature every morning before getting up |
| Follicular study (follicle tracking) | Ultrasound shows follicle growth and rupture | Done by gynaecologists/fertility clinics; common in India |
| Day-21 progesterone blood test | Confirms ovulation occurred | Timed ~7 days before your next period |
Tips when trying to conceive
- Have intercourse every 1–2 days during the fertile window – no need to time it to the hour.
- Start folic acid 400 micrograms daily at least one month before trying; it reduces the risk of neural tube defects.
- Get checked for anaemia, thyroid function and rubella immunity before conceiving.
- Maintain a healthy weight, limit caffeine, and avoid smoking, alcohol and tobacco (including gutkha and pan masala) for both partners.
When to see a fertility specialist
See a gynaecologist if you haven’t conceived after 12 months of regular unprotected intercourse (or 6 months if you are 35 or older), if your cycles are shorter than 21 or longer than 35 days, or if you have a known condition such as PCOS, endometriosis or thyroid disease.
Calendar-based predictions are not a reliable form of contraception. If you want to avoid pregnancy, talk to a doctor about effective methods.
Frequently asked questions
How many days after my period do I ovulate?
In a 28-day cycle, about 14 days after your period starts. In a 32-day cycle it’s closer to day 18, and in a 24-day cycle around day 10.
Can I ovulate twice in one cycle?
More than one egg can be released within the same 24-hour window (which is how non-identical twins happen), but a second ovulation days later in the same cycle is not thought to occur.
Is ovulation calculator accurate for irregular periods?
Less so. If your cycle length varies a lot, use LH test strips or follicle tracking in addition to the calculator.
Can I get pregnant outside the fertile window?
Pregnancy is very unlikely outside the fertile window, but because ovulation can shift unexpectedly, the ‘safe days’ are never guaranteed.
Does PCOS affect ovulation?
Yes. PCOS often causes irregular or absent ovulation. Many women with PCOS conceive with lifestyle changes or ovulation-induction treatment from a gynaecologist.
Medical disclaimer: The results and information on this page are estimates for general education only. They are not a diagnosis and do not replace advice from your gynaecologist, obstetrician or midwife. If you have pain, bleeding, reduced baby movements or feel unwell, contact your doctor or call 108 immediately. Read the full disclaimer.
Sources & further reading
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. N Engl J Med 1995;333:1517–21.
- NHS (UK). Pregnancy tests; Ovulation; Your pregnancy and baby guide. nhs.uk
- Federation of Obstetric and Gynaecological Societies of India (FOGSI). Clinical practice recommendations. fogsi.org