Find out exactly how many weeks and days pregnant you are, your current trimester, and how many days remain until your due date.
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How pregnancy weeks are counted
Pregnancy is measured in weeks starting from the first day of your last menstrual period (LMP) — not from conception, which typically happens about two weeks later. A full-term pregnancy is commonly estimated as 40 weeks (280 days) from LMP, which is why “how many weeks pregnant” and “due date” describe the same timeline from different angles.
How to use the calculator
- Choose your dating method: use the first day of your last period, or switch to due date if that is the date you know.
- Enter the date: use the calendar field and check that the date is correct.
- Review the estimate: the calculator shows gestational weeks and days, estimated due date, trimester, and approximate days remaining.
Trimester breakdown
- 1st trimester: up to 13 weeks 6 days
- 2nd trimester: 14 weeks through 27 weeks 6 days
- 3rd trimester: 28 weeks onward
Frequently asked questions
Why does the doctor’s dating sometimes differ from mine?
If you’ve had an early ultrasound, your provider’s dating is usually based on fetal measurements, which can be slightly more accurate than LMP-based dating alone — especially if your cycles are irregular.
Can I calculate this from my due date instead of LMP?
Yes — switch the method to “due date” and the calculator will work backward to figure out how far along you are.
Is week 1 the same as being pregnant for a week?
Not exactly — week 1 and 2 are counted from your last period, before conception has typically occurred, which is a standard (if slightly confusing) convention in pregnancy dating.
Medical note: This calculator gives a general estimate only and is not medical advice. Your doctor or midwife may date your pregnancy differently, especially after an early ultrasound. Follow their guidance and contact them about any concerns.