Estimate Your Baby's Due Date
This pregnancy due date calculator estimates when your baby is due and how far along you are today. Choose how you want to calculate: from the first day of your last menstrual period (LMP), your conception date, or an IVF embryo transfer date. You will see your estimated due date, your current week of pregnancy and trimester, and a list of key milestone dates.
How Due Dates Are Calculated
Example: if the first day of your last period was January 1, 2026 and your cycle is 28 days, your estimated due date is Thursday, October 8, 2026. With a 32-day cycle, it moves 4 days later, to October 12.
Pregnancy is counted from the first day of your last period, about two weeks before conception, which is why you are considered "2 weeks pregnant" at conception.
- Last period (Naegele's rule): due date = first day of your last period + 280 days (40 weeks). If your cycle is longer or shorter than 28 days, the date is shifted by the difference.
- Conception date: due date = conception + 266 days (38 weeks).
- IVF transfer: due date = transfer date + 263 days for a day-3 embryo, or + 261 days for a day-5 blastocyst.
Pregnancy Trimesters
- First trimester: weeks 1 through 13.
- Second trimester: weeks 14 through 27. The anatomy ultrasound is usually done between 18 and 22 weeks.
- Third trimester: week 28 until birth. A baby is considered full term from 39 weeks.
Frequently Asked Questions
How accurate is a due date calculator?
It gives a reliable estimate, but only about 1 in 20 babies is born on the exact due date. Most are born within two weeks either side. An early ultrasound is the most accurate way to date a pregnancy, and your provider may adjust your due date based on it.
What if I don't know the date of my last period?
Use your conception date if you know it, or an IVF transfer date if that applies. Otherwise, your healthcare provider can estimate your due date with an ultrasound.
Why does cycle length change my due date?
The standard formula assumes ovulation on day 14 of a 28-day cycle. With longer cycles, ovulation usually happens later, so the due date moves later by the same number of days. Shorter cycles move it earlier.