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Due Date Calculator – Pregnancy Due Date & How Far Along
Due date and how far along you are from your last period, conception date, IVF transfer or ultrasound.
Calculated in your browser – nothing you enter is sent or stored.
When is my baby due? This due date calculator estimates your pregnancy due date from the first day of your last menstrual period (LMP), your conception date, an IVF embryo transfer or an early ultrasound. It also shows how far along you are today, your trimester and a week-by-week timeline of key prenatal milestones.
How to Use the Due Date Calculator
- Choose the method you know best. Most people use the first day of the last period.
- Enter the date. For the LMP method, adjust your average cycle length if it isn't 28 days.
- For IVF, choose whether the embryo was transferred on day 3, 5 or 6. For an ultrasound, enter the gestational age the sonographer gave.
How the Due Date Is Calculated
Pregnancy is counted from the first day of the last period, about two weeks before conception, and lasts an average of 280 days (40 weeks).
- Last period: due date = LMP + 280 days, plus (cycle length − 28) days for longer or shorter cycles. An LMP of March 2, 2026 gives a due date of December 7, 2026; with a 32-day cycle it moves to December 11.
- Conception date: due date = conception + 266 days (38 weeks).
- IVF transfer: due date = transfer date + 266 days − embryo age. A day-5 blastocyst transferred on March 30, 2026 gives a due date of December 16, 2026.
- Ultrasound: the gestational age on the scan date is counted forward to 40 weeks. First-trimester scans are the most accurate, within about 5–7 days.
This is the same method doctors use (sometimes called Naegele's rule: add one year, subtract three months and add seven days to the LMP, which gives nearly the same date).
Weeks, Trimesters and Term
| Stage | Weeks of pregnancy |
|---|---|
| First trimester | Week 1 through 13 weeks 6 days |
| Second trimester | 14 weeks through 27 weeks 6 days |
| Third trimester | 28 weeks until birth |
| Early term | 37 weeks 0 days – 38 weeks 6 days |
| Full term | 39 weeks 0 days – 40 weeks 6 days |
| Late term | 41 weeks 0 days – 41 weeks 6 days |
These are the definitions used by the American College of Obstetricians and Gynecologists (ACOG). Babies born before 37 weeks are preterm.
How Accurate Is a Due Date?
A due date is an estimate. Only about 1 in 20 babies is born on it; most arrive within two weeks before or after. If an early ultrasound and your LMP date differ by more than about a week, your provider will usually go by the ultrasound. Your due date is set at your first prenatal visit and normally doesn't change after that.
Trying to conceive? The ovulation calculator predicts your fertile days.
Sources
- ACOG – Methods for estimating the due date (Committee Opinion 700)
- ACOG – Definition of term pregnancy
- MedlinePlus (NIH) – Pregnancy
Last reviewed: October 2026 by the ShrinkBee team. This calculator is for information only and does not replace care from your doctor or midwife.
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