How many weeks pregnant am I?
Enter the first day of your last menstrual period (LMP)
to estimate your gestational age in weeks and days,
along with your due date.
Pregnancy weeks are counted from the start of your last
period, rather than from the day of conception.
Calculate your pregnancy weeks
Estimated gestational age
Enter the first day of your last period to see your estimated pregnancy weeks and due date.
What is gestational age?
Gestational age describes how far a pregnancy has progressed.
It is usually counted from the first day of the last menstrual
period and expressed in completed weeks and additional days.
How is gestational age calculated?
Count the calendar days between the first day of your last
period and the calculation date. Divide by seven:
the whole number gives completed weeks, and the remainder
gives additional days.
day of your last period, your estimated gestational age is
8 weeks and 3 days.
How is the estimated due date calculated?
This calculator adds 280 days, or 40 weeks, to the first day
of your last period. This method assumes a regular 28-day
menstrual cycle. The due date is an estimate of delivery,
not a guaranteed birth date.
Is gestational age the same as fetal age?
No. Gestational age starts at the last menstrual period.
Age from conception starts at fertilisation and is often
about two weeks shorter in a typical 28-day cycle.
The difference varies with ovulation timing.
What if my periods are irregular or I do not know my LMP?
An LMP-based estimate may be less reliable. A clinician can
use an early ultrasound to establish or confirm pregnancy
dating. For IVF pregnancies, dating uses the embryo’s age
and transfer date.
Why show pregnancy age in weeks instead of months?
Calendar months have different lengths. Weeks and days provide
a clearer way to describe pregnancy progress, so a month-based
estimate is less precise.
Does this calculator assess fetal size or weight?
No. It estimates pregnancy dating from your period date.
Assessing fetal growth requires measurements and clinical
interpretation.
Medical reference:
ACOG — Methods for Estimating the Due Date
.