Pregnancy Due Date Calculator

Find your estimated due date, current pregnancy week, and trimester.

Happy pregnant woman during maternity — Pregnancy typically lasts 280 days (40 weeks) from the first day of your last menstrual period.

Calculation method

First day of last menstrual period Cycle length (days, default 28)

Baby ultrasound scan during pregnancy — Ultrasound scans can accurately date your pregnancy, especially in the first trimester.

How to Use This Calculator

Choose your method: Select whether you know your last period, conception date, or ultrasound result.
Enter the date: Fill in the relevant date field accurately. For LMP, also adjust cycle length if not 28 days.
Click Calculate: The tool instantly shows your estimated due date, current week, days remaining, and trimester.
Note the trimester: Your pregnancy is divided into three stages, each with different milestones.
Consult your doctor: This calculator provides an estimate — your healthcare provider confirms the due date.

Understanding Trimesters

1st (wks 1–13) 2nd (wks 14–27) 3rd (wks 28–40)

A full-term pregnancy is 40 weeks (280 days) from your LMP. Most babies are born between weeks 37 and 42. Only about 5% of babies are born exactly on their due date — it's an estimate, not a deadline.

The Naegele's Rule (the standard formula) adds 280 days to your LMP. If your cycle differs from 28 days, the calculator adjusts accordingly by adding or subtracting the difference.

Newborn baby at hospital after birth — Full-term births typically occur between weeks 37 and 42 of pregnancy.

Trimester and Milestone Reference Table

Weeks pregnant	Stage	What's typically happening
1–13	1st Trimester	Conception, implantation, major organ formation, morning sickness common
14–27	2nd Trimester	"Golden period" — energy often returns, anatomy scan around week 20
28–36	3rd Trimester	Rapid weight gain, more frequent prenatal visits, baby turns head-down
37–38	Early term	Baby is considered safe to deliver, though full development continues
39–40	Full term	Optimal delivery window; most babies are born in this range
41–42	Late/Post-term	Doctors often discuss induction if labor hasn't started naturally

Tips for Using This Calculator Accurately

Use your actual cycle length, not the default 28 days. Longer or shorter cycles shift ovulation, and therefore your due date, by several days.
An early ultrasound overrides LMP dating. If you have a first-trimester scan, your doctor will usually use that date instead of the LMP-based estimate, since it is more accurate.
Don't panic about the exact date. Only about 5% of babies arrive on their due date — think of it as the center of a 3–4 week window (37–42 weeks) rather than a deadline.
Track symptoms alongside dates. Pairing your calculated week with common trimester milestones (see table above) helps you know what prenatal tests or appointments to expect next.
Re-check after every scan. If a later ultrasound changes your estimated date by more than a few days, update your calculation and inform your care provider.

Frequently Asked Questions

How accurate is the due date calculator?

The estimated due date (EDD) based on LMP is accurate within 1–2 weeks for most women with regular cycles. An early ultrasound (before 14 weeks) is the most accurate dating method, with a margin of ±5–7 days.

What if my cycle is not 28 days?

This calculator adjusts for cycle length. If your cycle is 30 days, ovulation typically occurs on day 16 instead of day 14, so the due date shifts by 2 days. Enter your actual average cycle length for a better estimate.

What is gestational age vs. fetal age?

Gestational age counts from the first day of your LMP — so you are 2 weeks "pregnant" at the moment of conception. Fetal age (embryonic age) counts from conception and is always about 2 weeks less than gestational age.

Can I use this after a positive pregnancy test?

Yes. Enter the first day of your last period (before the missed period). Most home tests are taken around week 4–5 of gestational age.

What is the difference between due date and term?

Your due date is the 40-week mark. Full term is 39–40 weeks; early term is 37–38 weeks. Babies born at 37+ weeks are considered term and generally healthy. Pre-term is before 37 weeks.

Why did my due date change between visits?

Early ultrasounds (before 14 weeks) are the most accurate dating tool, so doctors often adjust the due date after the first scan if it differs from the LMP-based estimate by more than 5–7 days. Later scans are less reliable for dating because babies grow at different rates in the third trimester.

Related Health Calculators

⚖️ BMI Calculator 🍎 Calorie Calculator ⚖️ Ideal Weight 🎂 Age Calculator 🔥 BMR Calculator 📅 Date Difference 🏥 All Health Calculators