Due Date Calculator
Calculate your baby's due date from last menstrual period or conception date. See trimester milestones.
Estimated Due Date
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Weeks Remaining —
2nd Trimester Starts —
3rd Trimester Starts —
How to Use This Calculator
Choose whether to calculate from your last menstrual period or conception date, then enter the date. The calculator shows your due date, weeks remaining, and when each trimester begins.
Formula
From LMP: Due Date = LMP + 280 days
From Conception: Due Date = Conception + 266 days
From Conception: Due Date = Conception + 266 days
Example
Example: LMP of March 1, 2026: Due date = December 6, 2026. 2nd trimester starts June 1, 3rd trimester starts August 29.
Frequently Asked Questions
- LMP (Last Menstrual Period) is the first day of your last period. Conception typically occurs about 14 days later. If calculating from conception, 266 days are added instead of 280.
- Yes. An ultrasound in the first trimester may adjust your due date if measurements differ significantly from the LMP-based estimate.
- An early ultrasound (before 12 weeks) can estimate gestational age accurately. Your doctor can calculate the due date from the ultrasound measurements.
- Not quite. 40 weeks equals about 9 months and 7 days. Pregnancy is counted from the LMP, which is roughly 2 weeks before conception.