Current Week: Your gestational age, counted from the first day of your last period.
Trimester: Which of the three pregnancy stages you're in (1st: weeks 1-13, 2nd: 14-27, 3rd: 28-40).
Days Remaining: Approximate calendar days until your estimated due date.
Baby Size: A food-based size comparison for the current week of development.
Milestones: Key developmental events happening around this stage of pregnancy.
You enter either your due date directly or the first day of your last menstrual period (LMP). If you provide the LMP, the tool adds 280 days to estimate the due date. It then calculates your current gestational week by working backward from the due date, determines your trimester, and matches the week to a developmental milestone and a size comparison from standard prenatal references.
Gestational age counts from the last menstrual period (LMP) because it's an objective, easily remembered date. Conception typically occurs 2 weeks after the LMP, so gestational age is 2 weeks longer than fetal age.
Due dates are estimates. Standard pregnancy is 280 days (40 weeks) from LMP, but most babies arrive within 2 weeks before or after. An ultrasound, especially in the first trimester, can refine the estimate.
Update the calculator with your new due date. Early pregnancy ultrasounds (before 14 weeks) are most accurate for dating. Later ultrasounds may show size variation but don't change the assigned due date in many cases.
Yes. Full-term pregnancy ranges from 37 to 42 weeks. Babies born in this window have the best outcomes. Pregnancies past 42 weeks may require intervention, so discuss with your provider if you reach that point.
Gestational age counts from the LMP and is about 2 weeks longer. Fetal age counts from conception. Doctors use gestational age for screening, milestones, and viability assessments.
Estimate only. Results reflect your inputs and standard formulas — they are not financial, tax, legal, health, or investment advice. Verify important decisions with a qualified professional.