Due Date Calculator
Calculate your pregnancy due date based on your last menstrual period
Enter the first day of your last menstrual period to calculate your due date.
What is a Due Date Calculator?
A pregnancy due date calculator estimates when your baby will be born based on the first day of your last menstrual period (LMP). It uses Naegele's rule — adding 280 days (40 weeks) to the LMP — which is the standard method used by healthcare providers worldwide. Only about 5% of babies are born on their exact due date, but it provides an important reference point for prenatal care.
How to Use the Due Date Calculator
- Enter the first day of your last menstrual period (LMP)
- Your estimated due date is calculated instantly using Naegele's rule
- View your current week of pregnancy and days remaining
- See key milestones including trimester dates and important appointments
Features
- Calculates due date using Naegele's rule (LMP + 280 days)
- Shows current week and days pregnant
- Displays all three trimester start and end dates
- Highlights key milestones: heartbeat, anatomy scan, viability
- 100% private — no data sent to any server
Frequently Asked Questions
How accurate is the due date calculator?
The calculator uses Naegele's rule, which assumes a 28-day cycle with ovulation on day 14. Women with irregular cycles may have different actual due dates. An ultrasound in the first trimester provides the most accurate dating.
What are the three trimesters?
The first trimester covers weeks 1–13, the second trimester weeks 14–27, and the third trimester weeks 28–40. Each trimester brings distinct developmental milestones for the baby and physical changes for the mother.
What if I don't know my LMP date?
If you don't know your LMP, your healthcare provider can estimate your due date using an early ultrasound, which measures the baby's size to determine gestational age.