📌 Overview

Estimate your due date from the first day of your last menstrual period using Naegele’s rule, with current gestational age and trimester milestones.

👶 Pregnancy Due Date Calculator

Estimate your due date from the first day of your last menstrual period using Naegele’s rule, with current gestational age and trimester milestones.

First day of last menstrual period

Average cycle length (days)

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📋 How to Use

Enter the first day of your last menstrual period.
Adjust cycle length if yours is not 28 days.
Click Calculate.
Review your estimated due date and current gestational week.

❓ FAQ

How accurate is a due date?

Only about 4% of babies arrive exactly on the estimated date. Roughly 80% are born within two weeks either side, which is why it is called an estimate.

What if my cycle is not 28 days?

The calculator adjusts for that. A longer cycle usually means later ovulation, which pushes the due date later by the same number of days.

❓ More Questions

Is the due date accurate?

Only about 4% of babies are born exactly on the due date, and about 80% arrive within two weeks before or after, so it is an estimated range, not a fixed date.

What if my cycle is not 28 days?

The tool adjusts automatically. A longer cycle usually means later ovulation, and the due date shifts later by the same number of days.

💡 Use Cases

📅

Plan Ahead

Know when to book leave and appointments.

🩺

Track Progress

See your current gestational week.

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Prepare

Line up trimester milestones.

🔗 Related Tools

📖 Deep Dive: Pregnancy Due Date Calculator

How the due date is calculated

The most common clinical method is Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period. It assumes a 28-day cycle with ovulation on day 14.

Adjusting for irregular cycles

If your cycle is 32 days, ovulation is about 4 days later, so the due date shifts later by the same amount. This tool has that correction built in: due date = last period + 280 days + (cycle length - 28).

The three trimesters

First trimester: weeks 1-13, the critical period of organ formation.

Second trimester: weeks 14-27, symptoms usually ease and it feels most comfortable.

Third trimester: weeks 28-40, the fetus gains weight rapidly.

Important note

Actual delivery varies greatly between individuals; an ultrasound (especially in early pregnancy) is more accurate than menstrual dating. This tool is for reference only; follow your doctor's diagnosis for prenatal scheduling.