Pregnancy Due Date Calculator

The standard method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle is longer or shorter than 28 days, the estimate is shifted by the difference, because ovulation is assumed around 14 days before your next period. This calculator also supports three other dating methods: conception date (+266 days), IVF embryo transfer date (+263/+261/+260 days for day-3/day-5/day-6 embryos), and ultrasound dating.

Naegele's rule estimates the due date from the last menstrual period. The classic version is: LMP + 1 year, minus 3 months, plus 7 days. The day-accurate version used by this calculator simply adds 280 days to the LMP (adjusted for cycle length). The two versions can differ by a day or two because calendar months have uneven lengths; the 280-day version is more precise.

Add 266 days (38 weeks) to the conception or ovulation date. Human gestation averages 266 days from fertilization, versus 280 days from the last menstrual period — the 14-day difference is the typical follicular phase before ovulation.

Add a fixed offset to the embryo transfer date based on the embryo's age at transfer: 263 days for a day-3 embryo, 261 days for a day-5 blastocyst, or 260 days for a day-6 blastocyst. This works because gestational age at transfer is 17, 19, or 20 days respectively (14 days of follicular phase plus the embryo's age).

Yes. A first-trimester ultrasound measuring crown-rump length (CRL) is the most accurate way to date a pregnancy — more accurate than LMP when cycles are irregular or the LMP is uncertain. The math is simple: due date = ultrasound date + (280 − gestational age in days at the scan). Select the Ultrasound tab and enter your scan date plus the gestational age it showed.

Yes. Enter your average cycle length and the calculator adjusts the estimate: ovulation is assumed (cycle length − 14) days after your last period, so a 35-day cycle shifts the due date 7 days later than a 28-day cycle would. For very irregular cycles, dating by early ultrasound or known conception/ovulation date is more reliable — and your provider's clinical dating always takes precedence.

Use the "How far along am I?" tab: enter your last menstrual period (or a known due date) and the calculator shows your exact gestational age in weeks and days as of today, your current trimester, and how many days remain until the due date.

Counted from the last menstrual period: the first trimester runs from week 1 through week 13 (day 13w6d), the second trimester from week 14 through week 27, and the third trimester from week 28 until delivery. This calculator shows the exact calendar dates of each trimester for your pregnancy.

Early term is 37 weeks 0 days through 38 weeks 6 days, full term is 39 weeks 0 days through 40 weeks 6 days, late term is 41 weeks 0 days through 41 weeks 6 days, and postterm is 42 weeks and beyond. Birth before 37 weeks is considered preterm. Only about 5% of babies arrive on the estimated due date itself. Note: no date calculator can assess your personal risk of preterm labor — only your healthcare provider can evaluate that, so contact them promptly about any concerning symptoms such as regular contractions before 37 weeks.

Common milestones: heartbeat detectable around week 6, nuchal translucency screening at weeks 11–13, anatomy scan at weeks 18–22, age of viability at week 24, glucose screening at weeks 24–28, and Group B strep testing at weeks 35–37. This calculator personalizes every milestone to your own dates and can export them as calendar reminders. Typical symptom patterns by trimester: nausea and fatigue are most common in the first trimester, energy often returns in the second, and back discomfort plus frequent urination are common in the third — though every pregnancy is different.

They are estimates, not appointments: only about 5% of babies are born on the estimated due date, and anything from 38 to 42 weeks is within the normal range. Accuracy depends on the input — a known conception date or first-trimester ultrasound beats an uncertain last period, especially with irregular cycles. Treat the result as a planning anchor and confirm dating with your provider.

The Chinese gender predictor is a traditional chart that claims to predict a baby's sex from the mother's lunar age and lunar month of conception. There is no scientific evidence behind it — controlled checks put its accuracy at about 50%, the same as guessing. It is entertainment, not a diagnostic tool.

No. No due date calculator can determine a baby's sex — that information is not contained in any date. Fetal sex is typically identified at the anatomy ultrasound around weeks 18–22, or earlier via NIPT blood screening. Gender-prediction charts and old wives' tales are for fun only.

The anatomy (mid-pregnancy) ultrasound is usually scheduled between weeks 18 and 22, most commonly at week 20. The glucose screening test for gestational diabetes is usually done between weeks 24 and 28. This calculator computes your personal windows for both and includes them in the downloadable reminders.

Yes — completely free, no account and no signup, and designed to be one of the best and most complete pregnancy calculators online: four dating methods (most calculators offer only one), a personalized week-by-week timeline, and calendar reminders. It runs 100% in your browser: your dates are never uploaded anywhere, and the calendar file is generated locally on your device.

No. This tool is for information and planning only and is not medical advice. Clinical dating by your midwife or obstetrician — especially from a first-trimester ultrasound — always takes precedence. If your provider's dates differ from this calculator, follow your provider.