Pregnancy Due Date Calculator
Estimate your pregnancy due date and current week from your last menstrual period.
Fill in your details, then check your personalized result and recommendations.
Formula
Due date = last menstrual period + 280 days (40 weeks)
Worked example
LMP 30 days ago → about 4 weeks pregnant
What the pregnancy due date calculator does
This calculator estimates when your baby is likely to arrive and how far along you currently are, based on the first day of your last menstrual period (LMP). It also tells you which trimester you are in, which is helpful for tracking development milestones and appointments.
How the calculation works
It uses Naegele's rule, the standard clinical method, which adds 280 days — 40 weeks — to the first day of your last period. Because ovulation timing varies, the tool also adjusts for cycle lengths longer or shorter than the typical 28 days. Your current gestational age is measured in weeks from that same LMP date.
How to interpret your result
The due date is an estimate, not a deadline. A full-term pregnancy is anywhere from 37 to 42 weeks, and only a small fraction of babies are born on their exact due date. An early ultrasound, especially in the first trimester, provides the most accurate dating and may revise this estimate.
Health recommendations
Attend regular prenatal appointments, take recommended supplements such as folic acid, eat a balanced diet, and stay active as advised by your provider. This tool is for general guidance only and does not replace professional medical care during pregnancy.
FAQ
+How is a due date calculated?
By adding 280 days (40 weeks) to the first day of your last menstrual period (Naegele's rule).
+How accurate is the due date?
Only about 4% of babies arrive on the exact date; most are born within two weeks either side.
+What if my cycle isn't 28 days?
The estimate adjusts for cycle length, but an ultrasound gives the most accurate dating.