🤰 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.
Estimate your pregnancy due date based on last menstrual period or conception date. Get a week-by-week timeline with trimester breakdowns, current week details, and key milestones — all shown with clear progress indicators. Calculations follow standard 40-week obstetric guidelines. Your data never leaves your browser.
👆 Enter your dates above to calculate
📋 When to Use the Pregnancy Due Date Calculator
The Pregnancy Due Date Calculator is perfect for quick calculations when you don't have specialized software installed. Use it for personal finance planning, homework help, quick estimates during meetings, or verifying other calculations. It's designed for anyone who needs accurate, formula-based results instantly — students, professionals, freelancers, and curious minds. Because all math runs client-side in your browser, your inputs are never stored or transmitted, making it safe for sensitive financial or personal data.
⚙️ How the Pregnancy Due Date Calculator Works
The Pregnancy Due Date Calculator uses standard mathematical formulas implemented in JavaScript. When you enter your values and click Calculate (or as you type, for real-time tools), the browser performs the computation instantly using your device's processor. Results are displayed in a formatted output area. All calculations are stateless — when you close the tab, everything is gone. The tool uses Web APIs for storage (localStorage) to remember your preferences between sessions, but your calculation data is never persisted or transmitted.
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.