Pregnancy Week Calculator (current week + days)
Enter the first day of your last menstrual period (LMP). The calculator computes how many weeks and days pregnant you are right now, your trimester, due date, and how many days until birth.
- Trimester
- First (weeks 1-12)
- Estimated due date
- December 3, 2026
- Days until due date
- 210
- Total days pregnant
- 70
How it works
How pregnancy weeks are counted
Pregnancy is measured in 'gestational weeks' starting from the first day of your last menstrual period (LMP), not from conception. This is the standard clinical convention. So 'six weeks pregnant' means six weeks since LMP, or about four weeks since conception (since ovulation typically occurs around day 14 of the cycle).
Each week consists of 7 days, so '8 weeks 3 days' means 8 × 7 + 3 = 59 days since LMP. Doctors typically write this as 8w3d or 8+3. The 'count' increments at midnight each day — your week-and-day might shift by one calendar day depending on when LMP started.
Trimesters and what to expect
First trimester (weeks 1-12 or 13): the most rapid embryonic-to-fetal development. Morning sickness, fatigue, and food aversions are common. Risk of miscarriage is highest in this phase. First prenatal appointment usually happens around 8-10 weeks.
Second trimester (weeks 14-26): often called the 'easier' trimester — many of the early symptoms ease. Anatomy ultrasound around 18-22 weeks. First fetal movements ('quickening') typically felt 16-22 weeks. Energy returns for many people.
Third trimester (weeks 27-40+): rapid fetal growth and lung maturation. More frequent prenatal visits. Common new symptoms: heartburn, swelling, sleep disturbances. Most births happen between weeks 38 and 42; only ~4% on the exact due date.
When the LMP-based estimate may be off
Irregular cycles (variations of 7+ days from one cycle to the next) make LMP-based counting less reliable. First-trimester ultrasound (8-13 weeks) measures the embryo and back-calculates a more accurate gestational age. Trust the ultrasound dating if it differs from LMP by more than a week.
IVF pregnancies use a different convention: due date = embryo transfer + 263 days (3-day embryo) or + 261 days (5-day blastocyst). The LMP method doesn't directly apply.
If you don't know your LMP exactly (typical for those with irregular cycles or who weren't tracking), an ultrasound at any point can establish gestational age.
Frequently asked questions
›Why count from LMP, not conception?
It's the medical convention because conception date is rarely known precisely, while LMP is. The result is that 'gestational age' is about 2 weeks more than 'embryonic age'.
›What if I don't remember my LMP?
An ultrasound (especially in weeks 8-13) can establish gestational age accurately based on fetal measurements.
›How accurate is this?
Mathematically exact given an accurate LMP and a 28-day cycle. Real biology has variation, so the calculated due date is a best-estimate ±2 weeks.
›Why is my ultrasound week different?
Ultrasound measures the actual fetus and may reveal a different gestational age than LMP suggests, especially for irregular cycles. Trust the ultrasound for medical decisions.
›What does '38 weeks' mean for delivery?
37-42 weeks is full term. Births before 37 weeks are preterm; before 32 weeks are very preterm. After 42 weeks is post-term and labor is usually induced.
›When does each trimester start exactly?
First: week 1 to end of week 12 (or 13 in some conventions). Second: week 13 (or 14) through end of week 26 (or 27). Third: from week 27 (or 28) until delivery.
›Should I update my LMP if my doctor changed my due date?
Use the doctor's revised due date as your reference. You can back-calculate by subtracting 280 days, or just trust the doctor's app/chart for week tracking.
›Does the data leave my browser?
No. Calculation runs locally; nothing is sent to a server.
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