Pregnancy Due Date Calculator

Standard pregnancy calculations assume a 28-day cycle. If your cycle is longer (e.g., 30 days), ovulation occurs later, shifting your due date later. This calculator adds or subtracts days based on your actual cycle length for a more accurate estimate.

Use your average cycle length. If your cycles range from 26-30 days, use 28. If you have a regular cycle, use that number. Irregular cycles make due date prediction less accurate; ask your doctor for ultrasound dating in the first trimester.

Pregnancy is measured from the first day of your last menstrual period (LMP), not from conception. You're considered 2 weeks pregnant at conception. This calculator shows your gestational age (weeks since LMP).

Ultrasound dating, especially in the first trimester, is more accurate than calendar calculations. Differences of a few days are normal. If your ultrasound shows a significantly different date, use that for more accuracy.

Schedule your first prenatal appointment around 8-10 weeks of pregnancy (or as soon as you know you're pregnant). This appointment confirms your due date via ultrasound and establishes baseline health measurements.

First trimester ends at 13 weeks, second trimester at 27 weeks, third trimester at delivery. Viability (can survive outside womb) is around 23-24 weeks. Most babies arrive between 37-42 weeks, with 40 weeks as the standard due date.