How long does the fertile window last?

Sperm survive 3–5 days in the reproductive tract, and an egg is viable for 12–24 hours after release. This creates a fertile window of roughly 6 days — 5 before ovulation plus ovulation day itself.

Can I use this calculator for birth control?

No. This calculator estimates average ovulation but cannot account for cycle irregularities, illness, stress, or other factors that shift ovulation. It is not a reliable contraceptive method.

What if my cycle is irregular?

Use an average of your last 3 cycles. For highly irregular cycles, ovulation predictor kits (OPKs) that detect the LH surge, or basal body temperature (BBT) tracking, provide more reliable information.

TheCalci

Ovulation Calculator

First day of last period

Average cycle length(days)

Due Date Age Date Difference