Pregnancy Due Date Calculator
Calculate your pregnancy due date from last menstrual period.
How to use Pregnancy Due Date Calculator
Enter Your Last Menstrual Period Date
Click the date input field labeled 'Last Menstrual Period (LMP)'. Select the first day of your last menstrual cycle from the calendar picker. The date format is MM/DD/YYYY. Alternatively, type the date directly into the field.
Select Your Cycle Length (Optional)
Click the 'Cycle Length' dropdown menu showing the default value of 28 days. Choose your average menstrual cycle length from 21 to 35 days if different from standard. Leave as 28 days if unsure. Click the dropdown arrow to reveal all options.
Click Calculate Button
Press the blue 'Calculate Due Date' button below the input fields. The calculator processes your data instantly in your browser and displays results in the 'Results' section below.
View Your Estimated Due Date
Read your estimated due date displayed prominently in the results box. The calculator shows your due date in bold text, your current week of pregnancy, and conception date. Share or print the results using the buttons in the results section.
How to Calculate Your Pregnancy Due Date Online — Complete Free Guide 2026
Calculate Your Pregnancy Due Date in 60 Seconds
Determining your pregnancy due date is one of the first steps in prenatal care. Our free online Pregnancy Due Date Calculator gives you an instant estimate based on your last menstrual period (LMP)—no registration, no fees, completely private.
Your due date isn't a fixed deadline but rather an estimated window. Most babies arrive within 2 weeks before or after the calculated date. Healthcare providers typically use the first day of your last menstrual period as the starting point, counting forward 280 days (40 weeks) to estimate delivery.
Why Your Last Menstrual Period Matters
The first day of your last menstrual period is the standard reference point for calculating pregnancy length. This method, called Naegele's Rule, has been used for over 200 years and remains accurate within plus-or-minus 2 weeks for most pregnancies.
If you don't remember your exact LMP date, use your best estimate. Write down the approximate date and verify it at your first prenatal ultrasound, where your healthcare provider can confirm or adjust the due date based on fetal development measurements.
How to Use the Free Calculator
Step 1: Enter Your Last Menstrual Period Date Click the date field and select the first day of your last menstrual period from the interactive calendar. You can also type the date directly (MM/DD/YYYY format). This single piece of information is all you need.
Step 2: Set Your Cycle Length The calculator defaults to 28 days, the average menstrual cycle. If your cycle is typically shorter (21 days) or longer (35 days), select your actual length from the dropdown menu. This personalizes your due date calculation for better accuracy.
Step 3: Calculate Instantly Click the blue "Calculate Due Date" button. Your results appear instantly—no waiting, no confirmation emails, no data collection.
Step 4: Review Your Results Your results show your estimated due date, current pregnancy week, trimester, and conception date. You can print or save these results for your healthcare provider.
Understanding Your Results
The calculator displays:
- Estimated Due Date: Your baby's expected arrival date (40 weeks from LMP)
- Current Week: How many weeks pregnant you are today
- Trimester: Which trimester you're currently in
- Conception Date: Approximate date of conception (roughly 2 weeks after LMP)
Remember: Only about 5% of babies are born on their exact due date. Due dates are estimates, not predictions.
Factors That Affect Due Date Accuracy
More Accurate:
- You have a regular 28-day cycle
- You're certain of your LMP date
- You know your conception date
- You've had an early ultrasound (before 13 weeks)
Less Accurate:
- Irregular cycles (21-35 days variability)
- Uncertain LMP date
- Conditions like PCOS affecting ovulation
- Recent hormonal contraceptive use
First-trimester ultrasound dating (before 13 weeks) is considered the most accurate method, with a margin of error of only ±3 days. Always confirm your due date with your healthcare provider.
Pregnancy Timeline from Due Date
Once you know your due date, you can plan your pregnancy timeline:
- First Trimester: Weeks 1-13 (organ development)
- Second Trimester: Weeks 14-27 (rapid growth)
- Third Trimester: Weeks 28-40 (final development)
- Preterm Labor: Before 37 weeks
- Full Term: 37-40 weeks
- Overdue: After 42 weeks (medical intervention typically recommended)
Privacy & Security
Our free pregnancy calculator processes all data in your browser. Nothing is stored, logged, or shared. Your medical information stays completely private.
When to Contact Your Healthcare Provider
Use this calculator as a starting point, but always confirm your due date with your doctor. Seek medical care if you experience:
- Vaginal bleeding or spotting
- Severe abdominal pain
- Dizziness or fainting
- Signs of infection (fever, chills)
Final Thoughts
Knowing your due date helps you prepare physically and emotionally for your baby's arrival. Use our free Pregnancy Due Date Calculator today to get your personalized estimate. Share your due date with family, plan your maternity leave, and start your pregnancy journey with confidence.
Calculate your due date now—it takes just 60 seconds and requires no registration.