🤰 Pregnancy Due Date Calculator

Estimate your due date, track your pregnancy week by week, and know which trimester you're in — all in your browser.

First day of your last menstrual period

Date of ultrasound

Gestational age from ultrasound (weeks + days)

Weeks

Days

👆 Enter your dates above to calculate

⚕️ Disclaimer: This is an estimate based on standard pregnancy dating methods. Every pregnancy is unique. Always consult your healthcare provider for personalized medical advice.

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📋 When to Use the Pregnancy Due Date Calculator

The Pregnancy Due Date Calculator is ideal for expectant parents who want to track their pregnancy timeline and estimate their due date using medical-standard calculations. Use it to understand your pregnancy progress week by week, know which trimester you're in, and see key milestones like your estimated conception date. It's helpful for anyone who wants to stay informed between doctor visits — whether you're newly pregnant and curious or tracking your countdown to delivery. Because all calculations run client-side in your browser, your health information is never stored or transmitted.

⚙️ How the Pregnancy Due Date Calculator Works

The Pregnancy Due Date Calculator uses Naegele's rule (LMP + 280 days) as the primary dating method, with an ultrasound dating option that works backward from scan measurements. When you select the LMP tab and enter your last period date, the calculator adds 280 days to estimate your due date. For ultrasound dating, it subtracts the reported gestational age from the scan date to determine the LMP, then applies the same 280-day rule. The tool also calculates your current pregnancy week, days remaining, trimester, and a visual progress tracker — all running instantly in your browser using JavaScript.

How to Use the Pregnancy Due Date Calculator

Choose your dating method — select "Last Period (LMP)" if you know the first day of your last menstrual period, or "Ultrasound Dating" if you have results from a scan.
Enter your date — for LMP, just pick the date. For ultrasound dating, enter the scan date and the gestational age in weeks + days from the report.
Review your estimated due date — the calculator applies Naegele's rule (LMP + 280 days) and shows your current week, days until due, trimester, and conception estimate.
Check your pregnancy progress bar — the visual tracker shows how far along you are with trimester markers highlighted.

Frequently Asked Questions

How accurate is the due date estimate?

Naegele's rule (LMP + 280 days) provides an estimate — only about 4% of babies are born on their exact due date. Most arrive within two weeks before or after. An early ultrasound (before 12 weeks) gives the most accurate dating, typically within ±5 days.

What if I don't know my LMP date?

Use the "Ultrasound Dating" tab. Enter the date of your earliest ultrasound scan and the gestational age (weeks + days) from the report. The calculator works backward from that scan to determine your estimated due date.

Is my data stored or shared?

No. All calculations run entirely in your browser. Your dates are saved to your device's localStorage only — nothing is sent to any server. You can clear the data at any time.

What does each trimester mean?

1st trimester: weeks 1–13 (organ development, highest miscarriage risk). 2nd trimester: weeks 14–26 (often the most comfortable period). 3rd trimester: weeks 27–40 (rapid growth, preparation for birth). The progress bar highlights which trimester you're currently in.