Health & Fitness
Estimate your due date using Naegele's rule. Enter your last menstrual period date and cycle length.
Estimated Due Date
Wednesday, January 13, 2027
175 days remaining
Naegele's rule estimates due date as LMP + 280 days, adjusted for your cycle length. This is an estimate; your healthcare provider will confirm with ultrasound.
A pregnancy due date calculator is a tool that computes your baby's expected arrival date using standard obstetric formulas. It works from either your last menstrual period (LMP)—the most common reference point—or your conception date. Healthcare providers worldwide use these calculations because the average pregnancy lasts 280 days (40 weeks) from the first day of your LMP.
The calculator applies Naegele's Rule, the standard obstetric formula: take your LMP date, add one year, subtract three months, then add seven days to get your estimated due date (EDD). If you provide a conception date instead, the tool adds 266 days. Most pregnancies deliver within two weeks of the due date (between 38 and 42 weeks), so the calculator shows your due date as a single point estimate alongside the normal delivery window.
EDD = LMP + 280 days (or LMP + 1 year − 3 months + 7 days)LMP is the first day of your last menstrual period. 280 days equals 40 weeks (the standard pregnancy length from LMP). If using conception date, add 266 days instead (since conception occurs roughly 14 days after LMP).
| Input | Result | Notes |
|---|---|---|
| LMP: January 15, 2024 | Due date: October 22, 2024 | Assuming a regular 28-day cycle; due date falls 40 weeks from LMP. |
| Conception date: February 10, 2024 | Due date: November 13, 2024 | 266 days from conception = approximately 38 weeks, accounting for the 2-week pre-conception offset. |
| LMP: June 1, 2024 | Due date: March 8, 2025 | Spans calendar years; calculator handles this correctly. |
Highly accurate for average 28-day cycles: about 90% of births occur within 2 weeks of the calculated due date. Ultrasound dating in the first trimester is even more precise (±3–5 days) and should confirm or adjust the calculator estimate.
Ask your healthcare provider to perform an early ultrasound (before 13 weeks), which can pinpoint your due date to within a few days. You can also try to reconstruct the date from a calendar, diary, or app that tracked your cycle.
Normal pregnancy length varies: some babies arrive at 38 weeks, others at 42 weeks, and both are considered full-term. The due date is a point estimate, but your baby could naturally arrive any time in that window.
Standard calculators assume a 28-day cycle. If yours is 30 days, for example, your actual due date may shift by 1–2 days. Discuss your typical cycle length with your provider if it differs significantly from 28 days.
Yes. The calculator will add 266 days (38 weeks) from conception, which accounts for the roughly 2-week gap between the start of your cycle and actual conception.
Going past your due date is common and usually safe, but your provider will monitor you closely. Induction or delivery is typically recommended by 42 weeks to reduce risks; always follow your doctor's guidance.