Date & Time Tools
Pregnancy Due Date Calculator
Estimate a due date, conception date and gestational age from LMP, a known due date or conception using Naegele’s 280-day rule.
Dates
Start from
Results
Estimated due date
2026-10-22
Gestational age
34w 2d
Trimester
Third trimester
Estimated conception
2026-01-29
Days remaining
40
This is Naegele’s 280-day estimate, not a medical diagnosis. Cycle length and ultrasound dating can move the due date.
About this tool
The common due-date estimate is Naegele’s rule: 280 days (40 weeks) after the first day of the last menstrual period. Conception is estimated 14 days after that LMP, which assumes a 28-day cycle.
How to use
- Start from LMP, a known due date, or an estimated conception date.
- Change the “As of date” to see gestational age on that day.
- Read due date, conception estimate, trimester and days remaining.
Formula and methodology
Due date = LMP + 280 days. Conception estimate = LMP + 14 days. Gestational age is the whole days from LMP to the “as of” date, shown as weeks + leftover days. Trimester 1 is days 0–90, trimester 2 is 91–188, trimester 3 is 189–280.
Worked example
LMP on 15 January 2026 gives a due date of 22 October 2026 and a conception estimate of 29 January 2026. On 12 September 2026 that pregnancy is 34 weeks and 2 days.
Frequently asked questions
Is this medical advice?+
No. It is a calendar estimate. Ultrasound dating, cycle length and clinical judgment can move the due date by days or weeks.
What if my cycle is not 28 days?+
Naegele’s rule assumes ovulation about 14 days after LMP. A longer or shorter cycle shifts conception. Use the conception mode if you have a better estimate.
Why is “today” a field instead of the clock?+
The page uses a fixed example date so the first render matches on the server and in the browser. Change “As of date” to any day you want.
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