Pregnancy Due Date Calculator

Calculate estimated pregnancy due date from last menstrual period

Pregnancy Details

First Day of Last Menstrual Period (LMP)

Enter the first day of your last period

Enter your LMP date and click Calculate

How to Use

Enter the First Day of Your Last Menstrual Period (LMP) using the date picker.
Optionally, enter your Average Cycle Length (default is 28 days) for a more personalised estimate.
Click Calculate to see your Estimated Due Date (EDD), current gestational week, and trimester milestones.
Use the trimester timeline to understand key dates for scans and check-ups.

How is the Due Date Calculated?

The standard method is Naegele's Rule: add 7 days to the first day of your LMP, then add 9 months (or subtract 3 months and add 1 year). This gives an Estimated Due Date (EDD) based on a 40-week (280-day) pregnancy from the LMP.

Pregnancy Timeline

Trimester	Weeks	Key Milestones
First	1 – 13	Organ formation, first ultrasound (8–12 weeks), NT scan
Second	14 – 27	Anatomy scan (18–20 weeks), foetal movement begins
Third	28 – 40+	Rapid weight gain, GBS test, birth preparation

Important Scans During Pregnancy (India)

Dating scan: 6–8 weeks (confirms pregnancy and dates it)
NT scan + double marker: 11–13 weeks (Down syndrome screening)
Anomaly scan: 18–20 weeks (structural defects check)
Growth scan: 28–32 weeks and again at 36 weeks

Disclaimer

This calculator provides estimates for informational purposes only. Always confirm your due date and pregnancy dating with your gynaecologist or via ultrasound. Do not make medical decisions based solely on calculator results.

Frequently Asked Questions

The LMP (Last Menstrual Period) method assumes a 28-day cycle with ovulation on day 14. It is accurate to ±1–2 weeks for most women. About 80% of babies are born within 2 weeks of the estimated due date. First-trimester ultrasound (crown-rump length measurement) gives better accuracy (±5–7 days) when cycles are irregular.

Naegele's rule is the formula used by virtually every doctor and calculator: add 7 days to the first day of your LMP, then subtract 3 months (or add 9 months). This gives the Estimated Due Date (EDD). Example: LMP = 1 January → EDD = 8 October of the same year.

First trimester: Weeks 1–13 (organ formation, highest miscarriage risk). Second trimester: Weeks 14–27 (foetal movement begins, generally the most comfortable period). Third trimester: Weeks 28–40+ (rapid growth, preparation for birth). Full term is 37–42 weeks; 40 weeks is the standard.

If your cycle is longer (e.g., 35 days), ovulation likely occurs later, pushing the due date forward. If shorter (e.g., 21 days), the due date moves earlier. Some advanced calculators adjust for cycle length. Always discuss irregular cycles with your gynaecologist — an early ultrasound is the most reliable dating method.

Most doctors consider 37–42 weeks as normal full-term. Going past 40 weeks is common — only about 5% of babies arrive on their exact due date. Most hospitals initiate monitoring or induction around 41 weeks. Never make medical decisions based solely on a calculator — always follow your doctor's advice.