Due Date Calculator
Estimate your baby due date using last menstrual period, conception date, or IVF transfer date.
How to Use the Due Date Calculator
- Select your calculation method: Last Period (most common), Conception Date, or IVF Transfer.
- Enter the relevant date based on your selected method.
- For LMP method, enter your average cycle length (default is 28 days).
- For IVF, select the embryo age at transfer (3-day, 5-day, or 6-day).
- Click Calculate to see your estimated due date and current gestational age.
Formula & Method
Naegele's Rule (LMP):Due Date = LMP + 280 days + (Cycle Length - 28)
Conception Date:Due Date = Conception Date + 266 days (38 weeks)
IVF Transfer:Due Date = Transfer Date + (266 - Embryo Age in days)
Gestational Age:Weeks = Days from LMP / 7
Examples
| Method | Input Date | Estimated Due Date |
|---|---|---|
| LMP (28-day cycle) | Jan 1, 2026 | Oct 8, 2026 |
| LMP (30-day cycle) | Jan 1, 2026 | Oct 10, 2026 |
| Conception Date | Jan 15, 2026 | Oct 8, 2026 |
| IVF 5-Day Blastocyst | Jan 10, 2026 | Oct 1, 2026 |
Frequently Asked Questions
How accurate is a due date calculator?
Only about 4% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the estimated due date. First babies often arrive 1-2 weeks late.
Why is my due date different from my doctor's?
Doctors may use ultrasound measurements in early pregnancy to adjust dates. IVF due dates are typically more accurate than LMP-based dates because the exact conception date is known.
Can my due date change during pregnancy?
Yes, especially if your first ultrasound shows the baby is smaller or larger than expected for the gestational age. This is normal and helps ensure the most accurate due date.
People Also Ask
How is due date calculated from last period?
Add 280 days (40 weeks) to the first day of your last menstrual period. This is called Naegele's rule and assumes a 28-day cycle.
How many weeks pregnant am I?
Pregnancy is counted from the first day of your last period, not conception. So at conception, you are already considered 2 weeks pregnant.
Can my due date be wrong by 2 weeks?
Yes, due dates are estimates. About 70% of babies are born within 10 days of their due date, but 10% arrive more than 2 weeks early or late.