Track your pregnancy week by week with a due date countdown, trimester timeline, baby development milestones, and key appointment dates.
The Pregnancy Countdown Calculator tracks your pregnancy progress based on your due date or last menstrual period (LMP). It shows your current week and day, trimester, days remaining, and key developmental milestones. The standard pregnancy is 40 weeks (280 days) from the first day of your last period.
Knowing your exact pregnancy week helps you understand what's happening developmentally, prepare for upcoming appointments, and track important milestones. Each trimester brings different changes, symptoms, and medical checkpoints. This calculator breaks it all down in an easy-to-follow timeline.
From the first heartbeat detection (~6 weeks) to viability (~24 weeks) to full term (~37 weeks), this tool shows where you are in the journey. It calculates from either your due date or LMP date, adjusts trimester boundaries automatically, and provides a week-by-week development summary. Check the example with realistic values before reporting. Use the steps shown to verify rounding and units. Cross-check this output using a known reference case.
Tracking pregnancy progress by the week helps you prepare for appointments, understand development, and know what to expect. This calculator provides a comprehensive timeline from LMP to due date. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation. Align this note with review checkpoints.
Due Date = LMP + 280 days. Current Week = (Today - LMP) / 7. Trimester 1: Weeks 1-12. Trimester 2: Weeks 13-27. Trimester 3: Weeks 28-40. Days Remaining = Due Date - Today.
Result: Currently 20 weeks, 3 days — Trimester 2
With a due date of Sep 15, 2025 and today being late April 2025, you're approximately 20 weeks and 3 days pregnant, in the middle of the second trimester with about 139 days remaining.
Pregnancy is counted from the first day of the last menstrual period (LMP), not from conception. This means "week 1" starts before ovulation and conception (which typically occur around week 2). By the time a pregnancy test is positive (~4 weeks), the embryo is only about 2 weeks old but is counted as 4 weeks gestational age.
First trimester (weeks 1-12): All major organs begin forming. Heartbeat detectable by week 6. Morning sickness common. Risk of miscarriage highest. Second trimester (weeks 13-27): Rapid growth, movement felt by week 16-20. Anatomy scan at 18-22 weeks. Often called the "golden trimester." Third trimester (weeks 28-40): Brain development accelerates. Lungs mature. Baby gains significant weight. Preparation for birth.
Week 6: heartbeat detectable. Week 12: end of first trimester, reduced miscarriage risk. Week 20: usually the halfway point and anatomy scan. Week 24: viability milestone. Week 28: third trimester begins. Week 37: full term. Week 40: due date. These milestones help track a healthy pregnancy progression.
The standard calculation adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). An ultrasound may adjust this date.
First trimester: Weeks 1-12. Second trimester: Weeks 13-27. Third trimester: Weeks 28-40. Each has distinct developmental milestones.
Only about 5% of babies are born on their exact due date. The due date is the midpoint of a normal delivery window (37-42 weeks).
Gestational age counts from LMP (includes ~2 weeks before conception). Fetal age counts from conception. Gestational age is 2 weeks more.
Medical viability is generally around 24 weeks, though outcomes improve significantly with each additional week. Full term is 37+ weeks.
If you know your conception date, add 266 days (38 weeks) for the due date. Or add 2 weeks to conception date to get the equivalent LMP date.