Due Date Calculator

📖 Tool Introduction

The Due Date Calculator helps women who are trying to conceive or are already pregnant estimate their baby's birthday from the first day of their last menstrual period. The widely used Naegele rule adds 280 days (40 weeks) to that first day to obtain the estimated due date, and this tool follows that rule exactly. Using today as the reference point, it computes the current gestational week and day, the total days pregnant, whether you are in the first, second or third trimester, and how many days remain until the due date. The result also lays out a full pregnancy milestone timeline: from the first ultrasound at six weeks confirming an intrauterine pregnancy, through the nuchal translucency scan at twelve weeks, Down screening at sixteen, the anomaly scan at twenty-four, entering the third trimester at twenty-eight, full term at thirty-seven, all the way to the due date at forty weeks. Each node is converted into its calendar date, and milestones already passed are greyed out so your prenatal schedule is clear at a glance. Every calculation runs locally in your browser, with no record and no upload of any obstetric information. The greyed-out dots for past milestones give you an instant sense of how far along you are, while the future dates help you book your NT scan, anomaly scan and glucose test without guessing the correct week. Because the gestational age is recalculated from today each time you open the tool, you can revisit it across the trimesters and watch the countdown shrink week by week, which turns a confusing calendar into a reassuring plan you can share with family members who also want to track the journey. It is especially useful during the first trimester, when the exact week is hard to keep in your head, and again near term, when the countdown becomes a daily reminder to pack the hospital bag and arrange maternity leave.

✨ Key Features

• Standard method: adds 280 days to the LMP, matching common obstetric practice
• Live gestational weeks: computes today's week-and-day and total days pregnant
• Trimester detection: automatically identifies early, middle or late pregnancy
• Milestone timeline: seven key checkpoints converted to dates, past ones greyed out
• Countdown: shows days remaining until the due date, and flags overdue status
• Privacy: all dates are computed only in your local browser, offline and unshared

📝 How to Use

1. Select the first day of your last period in the date picker
2. Click the Calculate button
3. Read the due date, current weeks, days pregnant and current phase
4. Scroll down the milestone timeline to compare each checkup date
5. Click Example to load 2026-01-10 and try it instantly

⚠️ Notes

• For reference: the due date is an estimate; birth within two weeks either way is normal, so follow your obstetrician
• Accurate date: choose the first day of your last period; irregular cycles may widen the error
• Future dates: an LMP later than today triggers a warning that the date is wrong
• Milestones: the checkup weeks are common guidance; follow your hospital's schedule
• Privacy: pregnancy data is computed only locally with no network request, so use it freely