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Pregnancy Due Date Calculator: Estimate Your Due Date

This free pregnancy due date calculator estimates your due date from the first day of your last menstrual period. It also shows how many weeks pregnant you are today, your trimester dates and an estimated conception date.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

A due date is an estimate of when a baby is expected to arrive, counted from the first day of the last period. It helps parents plan, and doctors use it to track growth and schedule tests. It is a guide, not a promise.

Enter the first day of your last period and your usual cycle length. The tool gives the estimated due date and where you are today.

How to Use This Tool

  1. Pick the first day of your last period.
  2. Enter your usual cycle length if it is not 28 days.
  3. Press Calculate.
  4. Read the due date, weeks pregnant and trimester dates.

How the Calculation Works

The due date is the first day of the last period plus 280 days, adjusted by (cycle length − 28) days. Conception is estimated 14 days after the period start, adjusted the same way. Weeks pregnant are the days since the period start divided by seven. The first trimester ends at 13 weeks and 6 days, the second at 27 weeks and 6 days.

Worked Example

With a last period starting on 1 March 2026 and a 28-day cycle, the due date is 6 December 2026. Conception was around 15 March 2026, the first trimester ends on 6 June 2026 and the second on 12 September 2026.

Common Uses

  • Early planning after a positive test.
  • Planning leave and appointments.
  • Sharing an estimate with family.
  • Checking weeks pregnant today.

Tips and Common Mistakes

  • An ultrasound dating scan can replace this estimate.
  • Irregular cycles make the estimate less reliable.
  • Talk to a healthcare professional for medical decisions.

Next, you may need the days until calculator, date add and subtract calculator, date difference calculator, sleep calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Naegele’s rule adds 280 days (40 weeks) to the first day of the last period. If your cycle is not 28 days, the date is shifted by the difference.
Only about 4 in 100 babies arrive on the due date. Most are born within two weeks either side. An early ultrasound can give a better estimate.
Pregnancy is counted as 40 weeks from the last period, which is about 38 weeks from conception.
No. It is an estimate. Always confirm dates and care with your doctor or midwife.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.