Due Date Calculator

Calculate your estimated pregnancy due date based on the first day of your last menstrual period (LMP).

Pregnancy Details

First Day of Last Period:

Cycle Length (days):

Your Pregnancy Timeline

Estimated Due Date

40 weeks from LMP

Conception Date

approximate

First Trimester Ends

week 13

Current Week

weeks pregnant

💡 Note: Only about 5% of babies are born on their exact due date. A pregnancy is considered "full term" anywhere from 37 to 42 weeks.

How Due Dates are Calculated

Most due dates are calculated using Naegele's Rule, which assumes a standard 28-day menstrual cycle with ovulation on day 14.

Due Date = First Day of Last Period + 280 days (40 weeks)

Or: LMP + 1 year - 3 months + 7 days

Pregnancy Trimesters

Trimester	Weeks	Key Developments
First	1 - 13	Major organs form, morning sickness common
Second	14 - 27	"Honeymoon phase", baby movements felt
Third	28 - 40	Rapid weight gain, lung development

Factors That Can Change Your Due Date

Irregular Cycles: If your cycle is longer or shorter than 28 days, ovulation happens later or earlier.
Ultrasound Dating: A first-trimester ultrasound is often more accurate than LMP dating.
IVF Pregnancies: Due dates are calculated from the embryo transfer date.

⚠️ Medical Disclaimer: This calculator provides an estimate only. Always consult with your obstetrician or midwife for medical advice and precise dating.

References

American College of Obstetricians and Gynecologists (ACOG). "Due Date Calculation." 2026.
Mayo Clinic. "Pregnancy Week by Week." 2026.