How to use this calculator
Select whether you want to calculate from your last menstrual period (LMP) or from a known due date. Enter the appropriate date and the calculator instantly shows your current gestational age in weeks and days.
The results include your trimester, estimated due date, days remaining until delivery, percentage of pregnancy complete, and a brief note about what developmental milestones are occurring at your current week.
Understanding pregnancy dating
Pregnancy is measured in gestational weeks starting from the first day of your last menstrual period. This means that during the first two weeks of pregnancy, you have not actually conceived yet. Conception typically occurs around week 2 or 3 of gestational age.
A standard pregnancy lasts 40 weeks (280 days) from LMP. The three trimesters divide this time into roughly equal thirds, each with distinct developmental stages and physical changes for the mother.
Frequently asked questions
How many weeks pregnant am I?
Count the days from the first day of your last period to today, then divide by 7. The remainder is your extra days. For example, 100 days equals 14 weeks and 2 days.
When is my due date?
Your due date is 280 days (40 weeks) after the first day of your last period. Your healthcare provider may adjust this based on ultrasound measurements, especially if your cycles are irregular.
What trimester am I in?
First trimester covers weeks 1 through 12, second trimester is weeks 13 through 26, and third trimester is weeks 27 through 40. Each has different symptoms and milestones.
Can my due date change?
Yes. If an early ultrasound (usually between 8 and 12 weeks) shows a different size than expected based on LMP, your provider may adjust your due date. Ultrasound dating in the first trimester is accurate to within about 5 days.
Is this calculator a substitute for medical advice?
No. This calculator provides an estimate using the standard 280 day formula. Always confirm your gestational age and due date with your healthcare provider, who can account for cycle irregularities and ultrasound measurements.