Ovulation Calculator

Estimate your ovulation date, fertile window and next period based on your cycle.

Cycle Details
days
days
Understanding Your Cycle
Phases of the menstrual cycle
  • Menstrual phase: Days 1-5 (approx) - your period
  • Follicular phase: From day 1 until ovulation - an egg matures
  • Ovulation: A single day when the egg is released, usually 12-16 days before your next period
  • Luteal phase: From ovulation until your next period - typically a fixed 12-16 days
Signs of ovulation
  • Change in cervical mucus (becomes clear and stretchy, like egg white)
  • Slight rise in basal body temperature (0.5-1°F / 0.3-0.5°C)
  • Mild one-sided pelvic pain (mittelschmerz)
  • Positive result on an ovulation predictor kit (LH surge)
  • Increased libido
Tips for trying to conceive
  • Have intercourse every 1-2 days during your fertile window for the best chance
  • Track several cycles to spot your personal pattern before relying on predictions
  • Consider OPKs or basal body temperature charting alongside this calculator
  • If you don't conceive after 12 months trying (6 months if over 35), speak to a doctor
Quick Tips
  • Most fertile in the 2-3 days before ovulation
  • Average cycle is 28 days, but 21-35 is normal
  • Track 3+ cycles for more accurate predictions
  • Stress and illness can shift ovulation timing
Related Tools

Frequently Asked Questions

Ovulation typically occurs around 14 days before your next period starts (the luteal phase, which is usually a fixed 12-16 days regardless of cycle length). This calculator subtracts your luteal phase length from your predicted next period date to estimate when you ovulate.

The fertile window is the span of days in your cycle when pregnancy is possible. Sperm can survive in the body for up to 5 days, and the egg survives roughly 12-24 hours after ovulation, so the fertile window is generally the 5 days before ovulation plus the day of ovulation itself.

Calendar-based predictions are estimates only. They work best for people with regular, consistent cycles. Stress, illness, travel, and many health conditions can shift ovulation earlier or later. For more precision, combine this calculator with ovulation predictor kits (OPKs), basal body temperature tracking, or cervical mucus monitoring.

No. This tool is for general information and family-planning guidance only and is not a reliable method of contraception. Fertile windows can vary cycle to cycle, and sperm can survive several days, making calendar-only methods unreliable for preventing pregnancy. Speak to a healthcare provider about effective contraception.

If your cycles are irregular (varying by more than 7-8 days), calendar predictions become much less reliable. Tracking basal body temperature, using ovulation predictor kits, or consulting a doctor or fertility specialist is recommended for irregular cycles.