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. Everything runs locally; nothing is uploaded.
FreeToolHub Pregnancy Due Date Calculator is a free browser-based tool — estimate your pregnancy due date (EDD) using Naegele's rule, adjusted for cycle length. No signup, no upload; everything runs locally in your browser.
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 weeks between the LMP and the EDD map to a fairly predictable checklist. First trimester (weeks 0–13): book the first prenatal visit, expect the dating ultrasound around weeks 8–12, and start a prenatal vitamin with folic acid. Second trimester (weeks 14–27): the anatomy scan lands near week 20, and this is the window to plan parental leave and confirm your coverage. Third trimester (weeks 28–40): the glucose screening happens around weeks 24–28, weekly visits begin around week 36, and the bag should be packed by week 37 — full term starts there. Because the calculator saves your inputs in your browser, a weekly recheck shows the progress bar advance and the countdown in weeks without re-entering anything. If today falls past the EDD, that is still within the normal 37–42-week window up to 42 weeks, when providers typically discuss induction.
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.
Ovulation shifts with cycle length, so the calculator adjusts the EDD by adding (your cycle length − 28) days — a 32-day cycle moves the due date about 4 days later. Enter your average over the last few months for the best estimate.
Yes — an ultrasound between weeks 8 and 14 measures the fetus directly and is more accurate than any LMP-based estimate. Providers usually adopt the ultrasound EDD when it differs by more than 5–7 days; your doctor's date then becomes the official one.
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