Estimate your due date from LMP, conception date, ultrasound, or IVF transfer. Shows current gestational week, trimester, key milestones and a pregnancy timeline.
Enter the first day of your last menstrual period. Due date is calculated with Naegele's rule: LMP + 280 days, adjusted for cycle length.
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Enter the date you believe conception occurred. Due date is conception + 266 days (38 weeks).
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Enter the date of your ultrasound scan and the gestational age measured at that scan. Ultrasound dating is most accurate in the first trimester.
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Enter your embryo transfer date. For a Day 3 embryo, due date = transfer + 263 days; for a Day 5 embryo, transfer + 261 days.
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Estimated due date
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Gestational age today
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Countdown
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Estimated conception
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Progress
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Pregnancy timeline
Key milestones
- End of 1st trimesterweek 13—
- Viabilityweek 24—
- End of 2nd trimesterweek 27—
- Early termweek 37—
- Full term (due date)week 40—
Medical disclaimer. This calculator provides estimates only. Only about 4% of babies are born on their exact due date. Ultrasound dating in the first trimester is more accurate than LMP-based dating. For individual medical advice, always consult your OB/GYN or midwife.
Frequently asked questions
Naegele's rule (LMP + 280 days) assumes a regular 28-day cycle with ovulation on day 14. If your cycle is shorter or longer, the cycle-length input corrects the estimate. LMP dating is reliable when you know the exact first day of your last period and your cycles are regular. If either of those is uncertain, an early ultrasound gives a more accurate date.
The three trimesters are commonly defined as: first trimester — weeks 1 to 13 (conception, early organ development); second trimester — weeks 14 to 27 (growth, movement, anatomy scan); third trimester — weeks 28 to 40+ (final growth, preparation for birth). Some clinicians use slightly different cut-offs, but these are the most widely used ranges.
Only around 4–5% of babies are born on their estimated due date. About half of pregnancies deliver within a week of the due date, and most within two weeks on either side. A baby is considered full term from 37 weeks and late term after 41 weeks.
Obstetric guidelines (ACOG, RCOG) recommend using ultrasound dating instead of LMP when the difference is greater than 5–7 days in the first trimester, 10–14 days in the second trimester, or 21 days in the third trimester. First-trimester ultrasound (especially crown-rump length measurement before 13 weeks) is the most accurate way to date a pregnancy.
In IVF, the exact date of fertilisation is known. A Day 3 embryo is 3 days past fertilisation at transfer, so due date = transfer date + (266 − 3) = +263 days. A Day 5 blastocyst is 5 days past fertilisation, so due date = transfer date + (266 − 5) = +261 days. IVF dating is therefore the most precise method of all.
Per ACOG definitions: 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; post term is 42 weeks 0 days and beyond. Labour induction is often discussed once you reach late term.