Down to the day
How many weeks pregnant am I?
The answer is almost always further along than people expect — pregnancy is counted from before you were pregnant. Enter your due date or your last period and get the real number.
This is general information, not medical advice. Every pregnancy is different, and yours is the one your provider knows.
Why you were two weeks pregnant before you were pregnant
Pregnancy is counted from the first day of your last period — about two weeks before conception actually happened. So at the moment of conception you're already considered "two weeks pregnant", and by the time a test turns positive you're usually around four.
It's a convention rather than a biological claim. The date of your last period is something most people can pin down; the exact day of conception usually isn't. Dating from a fixed, knowable day keeps everyone — you, your midwife, your scan report — working from the same number.
Gestational age gets written as completed weeks plus days, like 25w5d. That means 25 full weeks are behind you and you're partway through week 26.
Know your last period but not your due date? Use the due date calculator.
While you're here
How many weeks pregnant am I?
Count from the first day of your last menstrual period, not from conception. That means you are considered about two weeks pregnant at the moment of conception, which is why the number is often higher than people expect.
Why does pregnancy start counting before conception?
Dating from the last period is used because it is the date most people can identify reliably, whereas the exact day of conception usually is not known. It is a shared convention, not a claim about when pregnancy began.
What week does each trimester start?
The first trimester runs through week 13, the second from week 14 through week 26, and the third from week 27 until birth.
What does 25 weeks and 5 days mean?
Gestational age is given as completed weeks plus leftover days. At 25 weeks and 5 days you have completed 25 full weeks and are partway through week 26.