Gestational Age Calculator
Calculate gestational age in weeks and days from the last menstrual period.
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Your result
14 weeks
Gestational age (weeks)
AI explanation
Formula
Gestational age = days since last menstrual period / 7, as whole weeks and remainder daysWorked example
LMP 2026-01-01, 10 weeks later
| Field | Value |
|---|---|
| First day of last menstrual period | 01-01-2026 |
| As of date | 12-03-2026 |
| Gestational age (weeks) | 10 |
| Plus days | 0 |
Assumptions
- Gestational age is conventionally measured from the last menstrual period, not from conception (which is roughly 2 weeks later) — this is standard obstetric convention.
- Informational only.
Frequently asked questions
What is gestational age?
The medical term for how far along a pregnancy is, measured in weeks and days from the first day of the last menstrual period — this is the standard used by healthcare providers.
Is gestational age the same as fetal age?
No — fetal (or embryonic) age is measured from conception, roughly 2 weeks after the last menstrual period, so it's about 2 weeks less than gestational age at the same point in pregnancy.
Why is gestational age measured from the last period instead of conception?
The exact date of conception is often unknown, but the start of the last period is typically easy to identify, making it a more practical and consistent reference point.
Related calculators
Sources
- Methods for Estimating the Due Date — American College of Obstetricians and Gynecologists (ACOG). Effective 01-05-2017, reviewed 13-09-2026.
This calculator provides a general estimate only and does not constitute personalized medical advice. Always confirm dates with a qualified healthcare provider, especially if ultrasound dating is available.
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