Pregnancy Due Date Calculator — Free Online Tool
Estimate your due date from LMP or conception date. · No signup · Works on mobile
100% private: your data is processed in your browser. Nothing is uploaded to our servers.
How to use the pregnancy due date calculator
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Select your calculation method — last menstrual period (LMP) or conception date.
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Pick the date on the calendar and adjust your average cycle length if it isn't 28 days.
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See your due date, current week of pregnancy, trimester, and milestone timeline.
What does this tool do?
This free pregnancy due date calculator estimates when your baby will arrive. Enter the first day of your last menstrual period (or your conception date) to instantly see your estimated due date, how many weeks pregnant you are today, your current trimester, and key milestone dates.
How does the pregnancy due date calculator work?
It applies Naegele's rule — the medical standard: due date = first day of last menstrual period + 280 days (40 weeks). If you know your conception date, it adds 266 days instead. Cycle length adjustments shift the estimate for cycles longer or shorter than 28 days.
Frequently Asked Questions
How accurate is a due date calculation?
Only about 4–5% of babies arrive exactly on their due date, but roughly 90% are born within two weeks either side of it. A first-trimester ultrasound is the most accurate dating method (±5–7 days); the LMP method used here is the standard clinical starting point.
What if my cycles are irregular or longer than 28 days?
Naegele's rule assumes ovulation on day 14 of a 28-day cycle. If your cycle is 35 days, ovulation likely happens around day 21, pushing your due date about a week later. This calculator lets you set your cycle length to adjust for that — but confirm with an early ultrasound.
Is the pregnancy due date calculator really free?
Yes — 100% free with no hidden charges, trial limits, or premium tiers for core features. You don't need to create an account or enter an email address. The site is supported by non-intrusive display ads, which keeps every tool free for everyone.
Is my data private when using the pregnancy due date calculator?
Completely. The pregnancy due date calculator runs entirely in your browser using JavaScript — nothing you type or upload is sent to our servers. When you close the tab, your data is gone. This makes it safe for confidential documents, financial figures, and personal information.
Does the pregnancy due date calculator work on mobile phones?
Yes. The pregnancy due date calculator is built mobile-first and works on any phone or tablet with a modern browser — iPhone (Safari), Android (Chrome), and everything in between. The layout adapts to small screens, so buttons and inputs stay easy to tap on a 375px-wide display.
Do I need to install anything to use the pregnancy due date calculator?
No. The pregnancy due date calculator works directly in your web browser — no downloads, no extensions, no signup. Just open the page, use the tool, and get your result instantly. It works on Windows, macOS, Linux, ChromeOS, iOS, and Android.