Track Your Cycle.
Understand Your Body.
Women's Health, Made Simple.

Our pregnancy calculators use Naegele's Rule — adding 280 days to the first day of your last menstrual period (LMP) — a standard starting point for dating a pregnancy. It is an estimate: only about 4–5% of babies are born on their due date, and irregular cycles make the estimate less reliable. Your healthcare provider will usually confirm dating with an early ultrasound.

For the most accurate result, take a home pregnancy test on the first day of your missed period. Testing too early may give a false negative. Use first-morning urine for the highest hCG concentration. Our Implantation Calculator can help estimate the earliest possible test date.

Irregular periods can result from hormonal imbalances (PCOS, thyroid issues), significant weight changes, excessive exercise, high stress, perimenopause, or uterine abnormalities. Cycles consistently shorter than 21 days or longer than 35 days warrant a visit to your OB-GYN.

Your fertile window is the 6-day period when pregnancy is possible — the 5 days before ovulation plus ovulation day itself. To calculate it, subtract 14 days from your next expected period date to find your ovulation day. For example, if your cycle is 28 days and your last period started June 1, your next period is June 29, making June 15 your ovulation day and June 10–15 your fertile window. Use our free Ovulation Calculator for an instant result.

Polycystic Ovary Syndrome (PCOS) is estimated by the CDC to affect about 6–12% of women of reproductive age in the U.S. Common early signs include irregular or missed periods (cycles longer than 35 days), excess facial or body hair (hirsutism), acne along the jawline and chin, thinning hair on the scalp, weight gain — especially around the abdomen — and difficulty getting pregnant. PCOS is one of the most common causes of ovulation-related infertility. If you notice these symptoms, consult a gynecologist. Use our PCOS Symptom Checker to review symptoms commonly associated with PCOS — it cannot diagnose the condition.

The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). For example, if your LMP was January 1, your estimated due date is October 8. Only about 5% of babies are born exactly on their due date — most arrive within 2 weeks before or after. Our Pregnancy Due Date Calculator also accounts for IVF transfer dates and irregular cycles.

You can track ovulation without a kit by monitoring these natural signs: (1) Basal Body Temperature (BBT) — your temperature typically rises by roughly 0.3–0.5°C (about 0.5–1°F) after ovulation; track daily at the same time each morning. (2) Cervical Mucus — near ovulation it becomes clear, slippery, and stretchy like raw egg whites. (3) Calendar Method — ovulation typically occurs 14 days before your next period. (4) Mittelschmerz — mild one-sided pelvic pain during ovulation. Our Ovulation Calendar helps you estimate your fertile days from your cycle dates.