Due Date Calculator
Calculate your estimated due date based on your last menstrual period or conception date. Get week-by-week pregnancy timeline and trimester information.
Enter the first day of your last menstrual period
All calculations happen in your browser. No data is sent to any server.
Frequently Asked Questions
How is a pregnancy due date calculated?▾
The due date is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If using a conception date, 266 days are added instead.
How accurate is the due date calculator?▾
Only about 5% of babies are born on the exact due date. The estimated due date gives a midpoint — most babies arrive within two weeks before or after. An ultrasound in the first trimester can refine the estimate.
What is gestational age and how is it measured?▾
Gestational age counts from the first day of your last menstrual period, not from conception. It is expressed in weeks and days (e.g., 28 weeks 3 days) and is used to track pregnancy milestones.
What are the three trimesters of pregnancy?▾
The first trimester spans weeks 1-12, the second trimester covers weeks 13-27, and the third trimester runs from week 28 until birth around week 40. Each trimester has distinct developmental milestones.
Is my data safe when using this due date calculator?▾
Yes. All calculations happen entirely in your browser. No personal health data is ever sent to a server.