Ovulation Calculator: Find Your Ovulation Day & Fertile Window

Short answer: Ovulation is the release of a mature egg from the ovary, usually once per cycle, about 14 days before your next period.

A rise in luteinizing hormone (LH) triggers the dominant follicle to release the egg into the fallopian tube. The egg survives only 12–24 hours, so pregnancy is possible only when sperm are already waiting or arrive within that time. Knowing your ovulation date helps you time intercourse, IUI or other treatment.

Short answer: Your cycle has four phases: menstrual, follicular, ovulation and luteal. Ovulation sits between the follicular and luteal phases.

A longer or shorter cycle almost always means a longer or shorter follicular phase, so ovulation moves with it. That is why the calculator subtracts your luteal phase from your cycle length instead of assuming day 14.

Ovulation usually happens about 14 days before your next period, not 14 days after the last one. So we count back from your expected period date using your cycle length and luteal phase. The fertile window is the 5 days before ovulation plus ovulation day, because sperm can survive up to 5 days while an egg lives only 12–24 hours.

Short answer: Add your cycle length to the first day of your last period to find your next period, then count back your luteal phase (usually 14 days).

Formula: Ovulation date = first day of last period + (cycle length − luteal phase) days.

The calculator above does this for you, including a range if your cycle is irregular.

Short answer: About 6 days: the 5 days before ovulation plus ovulation day.

Sperm can survive up to 5 days in the reproductive tract, while the egg lives under 24 hours. Chances rise sharply in the 2 days before ovulation and on ovulation day itself, then fall to near zero soon after. If you are unsure of your date, start earlier rather than later.

Short answer: Ovulation moves with your cycle length: roughly day 8 in a 21-day cycle, day 15 in a 28-day cycle and day 22 in a 35-day cycle.

Day 1 is the first day of your period, and the table assumes a 14-day luteal phase. Cycles shorter than 21 or longer than 35 days deserve a medical check.

Short answer: Enter your shortest and longest cycle to get a range instead of a single date, and confirm with LH strips or a follicle scan.

If your cycle length changes every month, a single date is unreliable. Switch to Irregular periods above and enter your shortest and longest cycle from the last 6–12 months. The tool shows the widest window in which you could ovulate. Because that window is long, pair it with LH test strips or an ultrasound follicle scan.

Short answer: Stress, PCOS, thyroid or prolactin problems, weight changes, illness and travel can all delay or skip ovulation.

• Stress and poor sleep: raise cortisol, which can delay the LH surge.
• PCOS: follicles stall, so ovulation is late or absent. It is the most common cause of ovulatory infertility.
• Thyroid and prolactin disorders: both disrupt cycle length and are easy to test.
• Weight changes: being very underweight, overweight or losing weight rapidly affects hormones.
• Intense exercise, illness, travel and shift work.
• Coming off hormonal contraception: the first 1–3 cycles may be irregular.

Short answer: The clearest signs are egg-white cervical mucus, a positive LH test and a small rise in basal body temperature afterwards.

• Egg-white cervical mucus: clear, thin and stretchy.
• Positive LH test: ovulation typically follows within 24–36 hours.
• Basal body temperature rise of about 0.3–0.5°C after ovulation (it confirms, it does not predict).
• Mild one-sided pelvic pain (mittelschmerz), breast tenderness or light spotting.

Short answer: A follicle ultrasound is the most accurate, LH strips are the best home method, and a calculator is a starting estimate.

Best approach: use the calculator to know when to start testing, begin LH strips about 5 days before your estimated ovulation date, and track cervical mucus.

Short answer: Have intercourse every 1–2 days across your fertile window. The two days before ovulation and ovulation day give the highest chance.

1. Have intercourse every 1–2 days across the fertile window, starting about 5 days before ovulation.
2. Confirm with LH strips so you are not relying on dates alone.
3. Take a pregnancy test on or after the first day of your missed period (shown above).
4. Support your cycle: take folic acid, keep a healthy weight, avoid smoking and limit alcohol and caffeine.

Short answer: It is an estimate. No calculator can be fully accurate because ovulation timing varies from cycle to cycle.

• Works best when cycles are regular and you know your typical luteal phase.
• Less reliable with irregular cycles, PCOS, stress, recent contraception, breastfeeding or perimenopause.
• To improve accuracy, add LH strips, cervical mucus tracking or a follicle scan.

It should never be used as the only form of contraception.

Short answer: No. Timing, position and diet do not decide your baby’s sex, and sex selection is illegal in India.

There is no evidence that intercourse timing, position or diet changes your baby’s sex; each conception is close to a 50/50 chance. Sex selection is also illegal in India under the PCPNDT Act. What timing does change is your chance of conceiving at all.

Short answer: Fertility declines gradually from the early 30s and faster after 35, mainly because egg quantity and quality fall.

An AMH blood test and an antral follicle count show your ovarian reserve at any age and take about a day.

• Start folic acid 400 mcg daily, ideally at least a month before conceiving, after checking with your doctor.
• Check vaccinations (rubella, varicella, hepatitis B) and screen for anaemia, vitamin D and B12.
• Get diabetes, thyroid disease or hypertension under control and review your medications.
• Stop smoking, tobacco and vaping, and limit alcohol and caffeine. This applies to both partners.
• Get regular moderate exercise and 7–8 hours of sleep.

Short answer: Male factors contribute in about 40–50% of couples. A semen analysis is a simple first test.

A semen analysis is simple, painless and often the first test to do. For an accurate result, abstain from ejaculation for 2–7 days before giving the sample. Heat, smoking, alcohol, obesity and some supplements can lower sperm count and quality.

• Day 2–3 hormones: FSH, LH, oestradiol, plus AMH, TSH and prolactin.
• Pelvic ultrasound: checks the uterus, ovaries, PCOS pattern and antral follicle count.
• HSG or sonosalpingography: checks whether the fallopian tubes are open.
• Mid-luteal progesterone: confirms that ovulation occurred.
• Semen analysis for the partner.

• Ovulation induction (tablets or injections with follicle monitoring) for irregular or absent ovulation.
• IUI: prepared sperm is placed in the uterus at the time of ovulation.
• IVF/ICSI: for blocked tubes, severe male factor, low ovarian reserve, endometriosis or unexplained infertility.
• Fertility preservation: egg freezing if you want to delay pregnancy.

Short answer: Seek help after 12 months of trying if under 35, after 6 months if 35 or older, or straight away with irregular cycles or known conditions.

Seek advice after 12 months of trying if the woman is under 35, after 6 months if she is 35 or older, and straight away with irregular cycles, endometriosis, PCOS, previous pelvic surgery or a known male-factor concern.

• "Everyone ovulates on day 14." Only if the cycle is 28 days with a 14-day luteal phase.
• "You cannot get pregnant during your period." It is uncommon but possible, especially with short cycles.
• "Having sex every day lowers sperm quality." Daily intercourse is fine; every 1–2 days is a good rhythm.
• "Regular periods mean you ovulate." Not always: an anovulatory cycle can still bleed.

This page is for information only and does not replace medical advice.

• American College of Obstetricians and Gynecologists (ACOG)
• American Society for Reproductive Medicine (ASRM): optimizing natural fertility
• NICE: Fertility problems: assessment and treatment
• World Health Organization: laboratory manual for semen examination
• Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, India