Pregnancy due date calculator

How the due date is calculated

The standard method (Naegele's Rule) adds 280 days (40 weeks) to the first day of your last menstrual period. This is the same calculation your doctor or midwife uses for a first-trimester estimate when no ultrasound dating is available yet.

The 40-week count starts from your LMP — even though conception typically happens around week 2. So your "gestational age" as measured medically is always about 2 weeks ahead of your embryonic age.

Trimesters

• First trimester: Weeks 1–12 (LMP to ~84 days)
• Second trimester: Weeks 13–26 (~85 to ~182 days)
• Third trimester: Weeks 27–40 (~183 days to due date)

How accurate is this date?

Only about 4% of babies are born on their exact due date. The estimated due date (EDD) is the midpoint of a normal delivery window that typically spans from 38 to 42 weeks. An ultrasound in the first trimester provides a more accurate date when cycle length differs from the standard 28-day assumption.

Track the countdown with Left

Add your due date as a countdown in Left and pin it to your Home Screen or Lock Screen. Every morning you'll see exactly how many days remain — and after the birth, switch to Left's "Since" mode to track how many days old your baby is.