What are the three trimesters of pregnancy?

First trimester: Weeks 1–12. Second trimester: Weeks 13–27. Third trimester: Weeks 28–40. Each trimester brings different developmental milestones and physical changes.

Can I calculate due date from conception date?

Yes. Add 266 days (38 weeks) to your conception date to estimate your due date. This calculator supports both LMP and conception date methods.

🤰 Pregnancy Calculator

Pregnancy Due Date
Calculator

Find your estimated due date, current pregnancy week, trimester, and key milestone dates — instantly.

First day of last menstrual period (LMP)

Cycle length Average cycle is 28 days. Adjust if yours differs.

Calculation method

-- Estimated due date

Week -- of 40

-- Weeks pregnant

-- Days remaining

-- Trimester

Pregnancy progress 0%

Week 1 Week 12 Week 27 Week 40

Key pregnancy milestones

Conception est.

~2 weeks after LMP

First scan (recommended)

Weeks 10–13

Anomaly scan

Weeks 18–21

Full term window

Weeks 39–40

⚠️ This is an estimate only. Actual due dates vary — only 4–5% of babies arrive on their exact due date. Always confirm with your doctor or midwife. This tool is not a substitute for medical advice.

How is the pregnancy due date calculated?

The standard method is Naegele's Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle — if yours is different, the calculator adjusts accordingly.

If you know your conception or ovulation date, the calculator adds 266 days (38 weeks). For ultrasound-based dating, it works backward from your scan date and gestational age to find the equivalent LMP and due date.

📅 LMP method

Most widely used. Add 280 days to the first day of your last period. Adjusted for cycle lengths other than 28 days.

🧬 Conception date

If you tracked ovulation, add 266 days (38 weeks) from conception for your estimated due date.

🔬 Ultrasound dating

Enter your scan date and gestational age. The calculator back-calculates the LMP equivalent and derives the due date.

📊 Accuracy

Due dates are estimates. Only 4–5% of babies are born on their due date. Most are born within 2 weeks either side.

Frequently asked questions

How is pregnancy due date calculated?

The standard Naegele's Rule adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle. If your cycle is longer or shorter, the due date is adjusted by the difference in days.

How many weeks is a full-term pregnancy?

A full-term pregnancy is 40 weeks (280 days) from the LMP. Early term is 37–38 weeks, full term is 39–40 weeks, late term is 41 weeks, and post-term is 42+ weeks.

What are the three trimesters?

First trimester is weeks 1–12 (organ formation). Second trimester is weeks 13–27 (rapid growth, movement felt). Third trimester is weeks 28–40 (final development and birth preparation).

When should I have my first ultrasound scan?

The dating scan is typically recommended between weeks 10–13 to confirm gestational age and due date. An anomaly scan (morphology scan) is usually performed between weeks 18–21 to check fetal development.

What if my cycle is not 28 days?

Select your actual cycle length from the dropdown. The calculator adjusts the due date — for cycles longer than 28 days, ovulation occurs later and the due date is pushed forward. For shorter cycles, it moves earlier.