Gestational Age Calculator
Calculate how many weeks pregnant you are from LMP, ultrasound CRL, or IVF transfer date. Find trimester, days until due date, and preterm classifications.
Weeks Pregnant
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Trimester —
Days Until Due Date —
Extended More scenarios, charts & detailed breakdown ▾
Gestational Age
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Trimester —
Days Until Due —
Professional Full parameters & maximum detail ▾
Gestational Age
Gestational Age —
Trimester —
Days Until Due Date —
Fetal Status
Est. Fetal Weight (grams) —
Viability Status —
Term Classification —
How to Use This Calculator
- Enter the first day of your last menstrual period (LMP) year, month, and day.
- See how many weeks and days pregnant you are, your trimester, and days until due date.
- Use From Ultrasound tab to estimate gestational age from crown-rump length (CRL).
- Use From IVF Transfer for IVF pregnancies by entering the transfer date and embryo age.
- The Professional tier adds estimated fetal weight, viability milestone, and preterm classifications.
Formula
Gestational Age = (Today − LMP) ÷ 7 = weeks and days
Due Date = LMP + 280 days (Naegele's rule)
From CRL: Gestational Age (weeks) ≈ CRL (mm) + 6.5
Example
Example: LMP = January 1, 2025. As of March 26, 2025 = 84 days = 12 weeks 0 days pregnant (First Trimester). Due date: October 8, 2025 (196 days away).
Frequently Asked Questions
- Gestational age is measured from the first day of your last menstrual period (LMP), not from conception. A full-term pregnancy is 40 weeks (280 days) from LMP.
- Count the number of days from the first day of your last menstrual period to today, then divide by 7 for complete weeks. The remaining days give you weeks + days (e.g., "8 weeks and 3 days").
- Crown-Rump Length (CRL) is measured by ultrasound in the first trimester. The formula CRL (mm) + 6.5 = gestational age in weeks is used up to about 14 weeks, giving a close estimate.
- First trimester: weeks 1–13. Second trimester: weeks 14–27. Third trimester: weeks 28–40+. Each trimester has distinct fetal development milestones.
- Fetal viability (survival outside the womb with medical support) is generally considered at 24 weeks. Babies born at 24–28 weeks have increasing survival rates with NICU care.