Estimate your due date with Naegele\u2019s rule, plus gestational age and trimester — 100% private.
Naegele's rule gives an estimated due date. Only ~4% of babies arrive exactly on that date; a full-term birth ranges from 37 to 42 weeks. Your healthcare provider will confirm with ultrasound.
The estimated due date is 280 days (40 weeks) from the first day of your last menstrual period. Conception typically happens about two weeks later — around ovulation.
For a 28-day cycle. If your cycle differs, an adjustment of +(cycle − 28) days is applied — the calculator does this automatically.
Last menstrual period: March 10, 2026, average 28-day cycle.
Estimate your pregnancy due date (EDD) using Naegele's rule, adjusted for cycle length. See gestational age in weeks and days, trimester, and a 40-week timeline. 100% private.
This calculator estimates your pregnancy due date (EDD) using Naegele's rule — the standard clinical shortcut that adds 280 days (40 weeks) to the first day of your last menstrual period. Because cycles vary, it applies a correction for your average cycle length. Alongside the date, it reports your current gestational age in weeks and days, your trimester (first, second, or third), and an estimated conception date. A visual 40-week timeline shows where today sits between the last menstrual period and the estimated delivery date. All values are computed locally in your browser — private by design.
(1) Enter the first day of your last menstrual period and your average cycle length (default 28 days). (2) The tool adds 280 days plus a cycle adjustment — add (cycle − 28) days — to produce the estimated due date. (3) Gestational age counts the days since your last period in weeks and days, and the trimester follows from that: 1st through week 13, 2nd weeks 14–27, 3rd from week 28. (4) The timeline bar positions today against the key milestones. Because only about 4% of births land exactly on the EDD, treat the result as an estimate your provider will refine with an early ultrasound.
The standard Naegele's rule adds 280 days (40 weeks) to the first day of your last menstrual period. For cycles other than 28 days, an adjustment is applied automatically.
Only about 4% of babies are born exactly on their due date. A full-term birth ranges from 37 to 42 weeks, so treat the EDD as a target range, not a fixed day.
Gestational age is counted from the first day of your last period. The calculator shows your current week and day, your trimester, and how many weeks remain until the estimate.
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