Pregnancy Due Date Calculator
The Pregnancy Due Date Calculator estimates your baby's due date using Naegele's rule, based on either your last menstrual period or a known conception date. It also displays your current gestational age in weeks and days (shown once you're within the typical 40-week window), so you can track progress without doing the math yourself. It's a quick way for expecting parents or a clinic front desk to sanity-check a due date given verbally.
How This Tool Works
Choose whether you know your last menstrual period or your conception date, enter that date, and get your estimated due date and current gestational age.
Formula & Method
Naegele's rule: due date = last menstrual period + 280 days, or conception date + 266 days.
Example Calculation
A last menstrual period of January 1 gives an estimated due date of October 8 — 280 days later. If instead you know your conception date was April 1, it adds 266 days and estimates December 23 — the two methods agree once you account for the roughly two-week gap between LMP and conception.
Frequently Asked Questions
How accurate is Naegele's rule?+
It's a widely used estimate, but only about 5% of babies are born exactly on their calculated due date — most arrive within two weeks before or after.
What if my cycle isn't exactly 28 days?+
Naegele's rule assumes a 28-day cycle. If yours is longer or shorter, your actual due date may shift — an ultrasound dating scan is more precise for irregular cycles.
Should I confirm this with my doctor?+
Yes — this is an estimate for planning purposes only. Your healthcare provider will confirm your due date using clinical measurements and ultrasound dating.
What's the difference between calculating from my last period versus my conception date?+
Calculating from your last menstrual period (LMP) adds 280 days and is the standard method doctors use, since conception date is rarely known for certain. Calculating from a known conception date adds 266 days instead. Both methods should land on nearly the same due date if your cycle is close to 28 days.
Why does the calculator only show my gestational age sometimes?+
Gestational age (in weeks and days) only appears when your entered date falls within roughly the 300-day window around a typical pregnancy — otherwise the math wouldn't represent a real in-progress pregnancy.
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<a href="https://everyfix.net/tools/pregnancy-due-date-calculator/">Pregnancy Due Date Calculator</a> by <a href="https://everyfix.net">EveryFix</a>Related Tools
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