Pregnancy Due Date Calculator — Estimate Delivery Date Free

One of the first questions every expecting parent wants answered: when is the baby due? Our Due Date Calculator uses Naegele's rule — the same method used by doctors worldwide — to estimate your delivery date from either your last menstrual period or conception date, plus shows your current week, trimester, and pregnancy progress.

What Is a Due Date Calculator?

A due date calculator estimates the expected date of delivery based on the start of the last menstrual period (LMP) plus 280 days (40 weeks), or from the conception date plus 266 days (38 weeks). This is Naegele's rule, the standard method used in obstetrics.

How to Use Our Due Date Calculator

1. Choose whether to calculate from your last menstrual period or conception/IVF date.
2. Enter the relevant date.
3. The calculator shows your estimated due date, current gestational week and day, trimester, days remaining, and a progress bar.

Why Use a Due Date Calculator?

• Planning: A due date helps you prepare for maternity/paternity leave, nursery setup, and birth planning.
• Milestone tracking: Knowing your current week helps you follow fetal development guides and know when to expect key ultrasounds and tests.
• Trimester awareness: Each trimester has different symptoms, risks, and care recommendations. The calculator tells you where you are.
• Privacy: Calculate your due date without creating an account on a pregnancy app. Our tool runs entirely in your browser.

Common Use Cases

Newly pregnant individuals calculate their due date as soon as they get a positive test, often before their first prenatal appointment. This helps them start planning and understand their timeline.

Parents tracking their pregnancy week-by-week use the calculator to confirm which week they are in, cross-referencing with baby size comparisons and development milestones from pregnancy guides.

Tips and Best Practices

• Only about 5% of babies are born on their exact due date. A normal full-term delivery can occur anywhere from 37 to 42 weeks.
• First pregnancies tend to go slightly past the due date on average. Second and subsequent pregnancies are slightly earlier on average.
• Your doctor may adjust the due date based on an early ultrasound measurement, which can be more accurate than LMP-based calculations.

Ready to try it? Use our free Pregnancy Due Date Calculator now — no signup required, works entirely in your browser.

Frequently Asked Questions

How is a due date calculated?

The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). From a known conception date, add 266 days (38 weeks). Your doctor may adjust this based on early ultrasound measurements.

How accurate is the estimated due date?

Only about 5% of babies are born on their exact due date. A full-term pregnancy can range from 37 to 42 weeks. The estimated due date is the midpoint of a normal delivery window, not a precise prediction.

What are the three trimesters?

The first trimester is weeks 1-12, the second trimester is weeks 13-26, and the third trimester is weeks 27-40. Each has different developmental milestones, symptoms, and medical checkpoints.