Due Date Calculator
Calculate your estimated due date and important pregnancy milestone dates. Get accurate pregnancy timing based on your last menstrual period or conception date.
Calculate Your Due Date
Choose your calculation method:
How Due Dates Are Calculated
Due dates are calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This method, known as Naegele's Rule, is the standard used by healthcare providers worldwide.
- • LMP + 280 days = Estimated Due Date
- • Only about 5% of babies are born on their due date
- • Full term is 37-42 weeks
- • Most babies are born within 2 weeks of due date
Understanding Your Due Date
Your due date is an estimate, not a deadline. It gives you and your healthcare team a target for planning and monitoring your pregnancy.
Factors That Can Affect Your Due Date
More Accurate Dating Methods
- • Early ultrasound (before 20 weeks)
- • Known conception date (IVF pregnancies)
- • Regular menstrual cycles
- • Accurate LMP recall
Factors That May Vary Timing
- • Irregular menstrual cycles
- • First pregnancy (tend to go longer)
- • Previous pregnancy history
- • Multiple pregnancies (twins, etc.)
Frequently Asked Questions
How accurate is the due date calculator?
The calculator is very accurate when using your LMP date, with most babies born within 2 weeks of the calculated due date. Early ultrasounds can provide even more precise dating.
What if I don't remember my last period?
If you can't remember your LMP date accurately, your healthcare provider will use an early ultrasound to determine your due date. This is often more accurate than guessing your LMP date.
Can my due date change during pregnancy?
Yes, your due date might be adjusted based on early ultrasound measurements, especially if there's a significant difference from your LMP-based date. Changes are most commonly made in the first trimester.
What happens if I go past my due date?
Going past your due date is normal - about 50% of first-time mothers deliver after 40 weeks. Your healthcare provider will monitor you closely and may discuss induction around 41-42 weeks.