Ovulation Calculator & Fertility Window

It uses the calendar method: in a typical 28-day cycle, ovulation happens around day 14 (counting day 1 as the first day of your last period). The fertile window is the 5 days leading up to ovulation plus the day of ovulation itself — sperm can survive for 3–5 days, so intercourse during this window has the highest chance of conception. Enter your last period date and average cycle length, and the calculator computes your fertile window, ovulation day, and implantation date for the next 6 cycles.

Your most fertile days are typically the 3 days before ovulation plus ovulation day itself. For a regular 28-day cycle, that's roughly days 11–15 (counting day 1 as your first day of menstruation). For longer or shorter cycles, the fertile window shifts proportionally — this calculator does the math for your specific cycle length.

Implantation happens 6–12 days after ovulation, when a fertilised egg attaches to the uterine lining. The calculator estimates this window — useful if you're tracking for early pregnancy testing or noticing implantation symptoms (light spotting, mild cramping).

Home pregnancy tests detect the hCG hormone produced after implantation. Most tests are accurate from 7–10 days after ovulation, with the most reliable results 14 days after ovulation (around the time your next period would start). The calculator shows the earliest test date for each cycle so you don't test too soon.

No. It's an educational tool based on calendar averages. If you've been trying to conceive for over a year (or 6 months if you're over 35), or have known fertility concerns like PCOS, consult a gynaecologist or fertility specialist for personalised assessment.

In a 28-day cycle, ovulation is around day 14, about a week after a typical period ends. But it depends on your cycle length: ovulation happens roughly 14 days before your next period starts, so in a 32-day cycle it's nearer day 18. Enter your cycle length above and the calculator pinpoints it for you.

It's less likely but possible, especially with short cycles. Because sperm survive up to five days, intercourse late in your period could still reach an egg if you ovulate early. If you're avoiding pregnancy, don't rely on calendar timing alone.