Pregnancy Due Date Calculator
Estimate your baby's due date from your last menstrual period or conception date. See your current week, trimester, and key pregnancy milestones.
The first day of your most recent period.
About Pregnancy Due Date Calculator
Knowing your estimated due date is one of the first steps in pregnancy planning. It helps you track fetal development, schedule prenatal appointments, and prepare for your baby's arrival.
Naegele's Rule
This calculator uses Naegele's rule, the most widely used method for estimating a due date. It adds 280 days (40 weeks) to the first day of your last menstrual period. If you know your conception date, the calculator adds 266 days (38 weeks) instead, since conception occurs roughly two weeks into a typical cycle.
Pregnancy Timeline
Your results include the current week of pregnancy, which trimester you are in, and a visual timeline showing key milestones. These milestones include the estimated conception window, first heartbeat detection (around week 6), the anatomy scan window (weeks 18-20), the viability threshold (week 24), and full-term status (week 37).
Key Dates at a Glance
The calculator displays several important dates: your estimated conception date, the approximate date of first heartbeat detection, the gender/anatomy scan window, the viability milestone, the full-term date, and of course the estimated due date. These serve as a general guide for what to expect during pregnancy.
LMP vs. Conception Date
You can enter either your last menstrual period date or your conception date. The LMP option is the standard approach used by most doctors. The conception date option is useful if you know the exact date through methods like IVF or tracked ovulation.
Privacy
All calculations run entirely in your browser. Your personal data is never sent to any server or stored anywhere.
Frequently Asked Questions
How is the due date calculated?
This calculator uses Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). If you enter a conception date instead, it adds 266 days (38 weeks), since conception typically occurs about 14 days after the start of the LMP. This is the standard method used by most healthcare providers.
How accurate is the estimated due date?
Only about 4 to 5 percent of babies are born on their exact due date. Most births occur within a two-week window around the estimated date. The calculation assumes a regular 28-day menstrual cycle. If your cycles are longer or shorter, the actual date may differ. An ultrasound in the first trimester generally provides the most accurate dating.
What are the three trimesters of pregnancy?
The first trimester covers weeks 1 through 12 and includes early organ development. The second trimester spans weeks 13 through 26 and is when most women feel fetal movement for the first time. The third trimester runs from week 27 until birth (around week 40) and is focused on fetal growth and preparation for delivery.
What is the difference between gestational age and fetal age?
Gestational age counts from the first day of the last menstrual period, so it includes about two weeks before conception actually occurs. Fetal age (also called embryonic age) counts from the date of conception. Gestational age is the standard used by doctors and is typically about two weeks ahead of fetal age.
When should I see a doctor to confirm my due date?
It is recommended to schedule your first prenatal visit between weeks 6 and 8 of pregnancy. During this visit, your healthcare provider may perform an early ultrasound to confirm the gestational age and refine your due date. This calculator provides an estimate, but your doctor's assessment should be considered definitive.