Pregnancy Due Date Calculator
Example: LMP March 1 → Due date December 6 (40 weeks)
Calculate your estimated due date and see how far along you are in your pregnancy. Enter the first day of your last period or conception date to get your timeline and key milestones.
40-Week Pregnancy Timeline
Due Date
Weeks Pregnant
Trimester
Days Remaining
How We Calculate This
Uses Naegele's rule: Due date = LMP + 280 days. For conception date: Due date = conception + 266 days. Weeks pregnant calculated from LMP to current date.
Methodology last reviewed: June 2023. How SparkCalc works
Sources: ACOG Committee Opinion No. 700: Methods for Estimating the Due Date
Frequently Asked Questions
How is the due date calculated?
The due date is calculated as 280 days (40 weeks) from the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14.
How accurate is the due date?
Only about 5% of babies are born on their due date. Most are born within 2 weeks before or after. The due date is an estimate, not a deadline.
What if I conceived via IVF?
For IVF, use the conception date option and enter the embryo transfer date minus the embryo age (e.g., transfer date minus 5 days for a day-5 blastocyst).
When do the trimesters start?
First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Each trimester brings different development milestones.
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You might also find these calculators helpful: Age Calculator, and Date Calculator.
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This calculator provides an estimated due date only. Only about 5% of babies are born on their due date, and most are born within 2 weeks before or after. Actual due dates should be confirmed by your healthcare provider through ultrasound and other medical assessments.