How Far Along Am I Calculator

How the “How Far Along Am I” Calculator Works

Pregnancy is dated from the first day of your last menstrual period, not from conception — so “weeks pregnant” (gestational age) is simply the number of days from that date until today, written as weeks and days. This calculator counts that gap and tells you your current week, your trimester, and how much of the 40-week journey is behind you.

If you only know your due date, it works backwards: the due date is 280 days after the last period, so it subtracts 280 to find the start and measures from there. The first trimester runs through week 13, the second from week 14 to 27, and the third from week 28 to birth.

weeks pregnant = (today − first day of last period) ÷ 7

Note: these are estimates based on standard averages. Every pregnancy is different — your doctor or midwife, using an ultrasound, gives the most accurate dates.