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Pregnancy Due Date Calculator
Calculate your estimated due date based on the first day of your last menstrual period (LMP). Uses Naegele rule —the standard clinical method.
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Estimated due date
How the due date is estimated
Naegele rule: LMP + 280 days (40 weeks). Conception date + 266 days. First-trimester ultrasound more accurate than LMP. Only 5% of babies arrive on due date — 37-42 weeks is normal range.
Frequently asked questions
How accurate are the results?
Formulas used here are validated in population studies but cannot account for individual genetics, body composition, or medical conditions. Treat results as a starting point, not a medical diagnosis.
Should I consult a professional?
If you have specific health concerns, existing conditions, or are planning significant lifestyle changes, consult a qualified healthcare provider (doctor, dietitian, physiologist).
How often should I recalculate?
Recalculate when your weight changes more than 5%, activity level shifts significantly, or every 3-6 months for routine monitoring. Results are snapshots — your body changes daily.
About the Pregnancy Due Date
Free pregnancy due date calculator. Enter the first day of your last period to estimate your due date. Uses the clinically validated Naegele rule. The tool runs entirely in your browser, so nothing you enter is uploaded or stored.
How to use the Pregnancy Due Date
- First day of last period — enter your first day of last period.
Last updated
For general wellness information only, not medical advice — see our disclaimer.