Due Date Calculator
Calculate your estimated due date based on your last menstrual period or conception date.
Overview
A due date calculator helps you estimate when your baby will arrive by calculating 40 weeks from the first day of your last menstrual period (LMP). This is the most common method used by healthcare providers.
While only about 5% of babies arrive exactly on their due date, knowing your estimated due date helps you and your healthcare team track your pregnancy's progress and schedule important prenatal tests and appointments.
The calculator can also work backwards from your due date to estimate conception date, or calculate from your conception date if you know it (common with fertility treatments).
⚙️ How It Works
- •Standard method: Adds 280 days (40 weeks) to the first day of your last menstrual period
- •Naegele's Rule: Adds one year, subtracts three months, and adds seven days to your LMP date
- •Conception date method: Adds 266 days (38 weeks) to your known conception date
- •Ultrasound dating in first trimester is considered most accurate and may adjust your due date
📋 What You Need
- →First day of your last menstrual period (LMP)
- →Average length of your menstrual cycle (usually 28 days)
- →Or your conception date if known
- →Or ultrasound dating if available
📱 How to Use
- 1.Enter the first day of your last menstrual period
- 2.Enter your average cycle length if different from 28 days
- 3.The calculator will show your estimated due date
- 4.Your healthcare provider may adjust this date after your first ultrasound
- 5.Remember this is an estimate - babies come when they're ready!
📊 Understanding Your Results
- →Your due date is an estimate for when you'll reach 40 weeks of pregnancy
- →Full-term pregnancy is anywhere from 37-42 weeks
- →Early term: 37-38 weeks
- →Full term: 39-40 weeks
- →Late term: 41 weeks
- →Post term: 42+ weeks
- →Most babies are born within 2 weeks before or after the due date
⚠️ Limitations to Keep in Mind
- •Assumes a 28-day cycle with ovulation on day 14
- •Not accurate for irregular periods
- •First trimester ultrasound is more accurate (within 3-5 days)
- •Cannot account for individual variation in gestation length
- •IVF pregnancies use embryo transfer date for more accurate dating
💡 Helpful Tips
- ✓Get an early ultrasound (7-13 weeks) for most accurate dating
- ✓Keep track of your menstrual cycle dates
- ✓Don't stress if your baby comes a bit early or late
- ✓Your provider may adjust your due date after ultrasound
- ✓Plan for a window of time around your due date, not one specific day
This guide is for educational purposes. Calculator results are estimates and should not replace medical advice. Always consult your healthcare provider for personalized guidance.