Estimate your baby's due date from your last menstrual period, conception date, IVF transfer date or ultrasound scan, and see your current gestational age, trimester and key pregnancy milestones.
Last updated: July 2026 · Based on standard obstetric dating methods
Pick the dating method that matches the information you have.
Enter the relevant date and any extra details for that method.
We estimate your due date and current gestational age.
Get key pregnancy milestone dates and your trimester progress.
A due date, or "estimated date of delivery," marks the point at which a pregnancy reaches 40 weeks of gestation. It's an estimate based on average pregnancy length, not a guaranteed delivery date. Only a small percentage of babies are born exactly on their due date, most arrive within a two-week window around it.
Due dates are statistical estimates based on average gestation length, with natural variation between pregnancies.
An early ultrasound is generally considered the most accurate way to confirm gestational age.
Even as an estimate, a due date helps guide prenatal appointments, testing windows and milestones.
This calculator supports four common dating methods. All of them ultimately estimate a 280-day (40-week) gestation period measured from the first day of the last menstrual period, or an equivalent reference point.
Naegele's Rule: Due Date = LMP + 280 Days (Adjusted for Cycle Length)
The most common method. Adds 280 days to the first day of your last period, adjusted for cycles longer or shorter than 28 days.
Adds 266 days to your known conception date, useful if you tracked ovulation closely.
Adds 263 days for a Day 3 transfer or 261 days for a Day 5 blastocyst transfer, since embryo age is known precisely.
Uses the gestational age measured at an ultrasound scan to back-calculate your due date, often the most accurate early in pregnancy.
Pregnancy is typically divided into three trimesters, each spanning roughly three months and associated with different stages of development and common experiences.
| Trimester | Weeks | General Focus |
|---|---|---|
| First Trimester | Weeks 1 - 12 | Early development, first prenatal visits and initial screening tests |
| Second Trimester | Weeks 13 - 27 | Often called the most comfortable stage, anatomy scan occurs around week 20 |
| Third Trimester | Weeks 28 - 40+ | Rapid growth, more frequent checkups and preparation for delivery |
These general milestones apply to most pregnancies, though your healthcare provider's schedule may vary based on your individual situation.
| Milestone | Week | Why It Matters |
|---|---|---|
| End of First Trimester | 13 | Miscarriage risk drops significantly after this point |
| Anatomy Scan | 20 | Detailed ultrasound checks organ development and growth |
| Viability Milestone | 24 | Generally considered the threshold for potential survival outside the womb with intensive care |
| Third Trimester Begins | 28 | Checkups typically become more frequent |
| Full Term | 37 | Baby is considered full term and organs are generally mature |
This Pregnancy Due Date Calculator provides a general estimate based on standard obstetric dating formulas and the information you enter. It is not a diagnostic tool and does not replace prenatal care. Actual due dates should be confirmed and monitored by a qualified healthcare provider, particularly through early ultrasound dating. Please consult your doctor or midwife with any questions or concerns about your pregnancy.
Your due date is typically estimated as 280 days (40 weeks) from the first day of your last menstrual period, or an equivalent point derived from conception date, IVF transfer date or ultrasound measurements.
Early ultrasound dating and IVF transfer dating are generally considered the most precise, since the gestational age is known directly, while LMP-based dating depends on regular, well-tracked cycles.
If an early ultrasound measurement differs meaningfully from the LMP-based estimate, your healthcare provider may adjust your due date to the more accurate ultrasound dating.
Gestational age is measured from the first day of your last menstrual period, while fetal age (or conceptional age) is measured from the estimated date of conception, roughly two weeks later.
If you're unsure of your last menstrual period, an ultrasound dating scan, especially in the first trimester, provides a reliable alternative for estimating your due date.
Only around 5% of babies are born on their exact due date. Most deliveries happen within about two weeks before or after the estimated date.
Yes. This calculator is completely free and works on desktop, tablet and mobile devices.
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