Pregnancy due date calculator
Estimate your due date from your last period using Naegele's rule.
Estimated due date
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Est. conception
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Weeks pregnant
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Trimester
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Only about 5% of babies arrive exactly on their due date — most arrive within two weeks either side. Think of this as a planning window, not a deadline.
How Naegele's rule works
The rule adds 280 days (40 weeks) to the first day of your last period, assuming a fairly typical 28-day cycle. If your cycles run longer or shorter, the adjustment for cycle length shifts the estimate closer to your actual conception date. Also want to estimate your fertile window? Try the ovulation calculator.
This is an estimate. Your care provider's dating ultrasound is the most reliable way to confirm gestational age.