Gestational Age Calculator
Calculate how far along you are in your pregnancy using your due date, last menstrual period, or conception date.
Calculate Gestational Age
💡 What to Expect
Your pregnancy is in the early stages. Focus on taking prenatal vitamins, staying hydrated, and scheduling your first prenatal appointment.
How It Works
Gestational age is measured in completed weeks and days starting from the first day of your last menstrual period (LMP), not from the actual date of conception, which is the medical convention used by virtually all providers and due date calculations.
This calculator can determine gestational age from your LMP directly, from a known conception date (adding 2 weeks to account for the gap before conception), or from an ultrasound-confirmed due date.
It’s worth knowing that gestational age runs about 2 weeks ahead of fetal age (the baby’s actual age since conception), which is why a baby is sometimes described as “10 weeks pregnant” when the embryo itself is closer to 8 weeks old. Both numbers are correct, they’re just measuring from different starting points.
Frequently Asked Questions
What is gestational age?
Gestational age is the number of weeks and days you have been pregnant, calculated from the first day of your last menstrual period (LMP). A full-term pregnancy is typically 40 weeks (280 days). It is the standard method healthcare providers use to track pregnancy progress and schedule important milestones.
What is the difference between gestational age and fetal age?
Gestational age is calculated from the first day of your LMP (about 2 weeks before conception). Fetal age (or conception age) is calculated from the actual date of conception and is typically 2 weeks less than gestational age. Healthcare providers almost always use gestational age for consistency.
How accurate is gestational age calculation?
Accuracy depends on the method used. LMP-based calculation is most accurate for women with regular 28-day cycles. Early ultrasound measurements (first trimester) are considered the most accurate dating method. Due dates calculated from LMP may be adjusted after an ultrasound if there is a significant discrepancy.
How is the due date calculated?
The standard method is Nägele’s rule: add 280 days (40 weeks) to the first day of your last menstrual period. Alternatively, add 266 days (38 weeks) to the conception date. Your healthcare provider may adjust the due date based on early ultrasound measurements.
What if I don’t know my LMP or conception date?
If you know your estimated due date from an ultrasound or healthcare provider, you can use the Due Date method to calculate your current gestational age. Early ultrasound dating is very reliable and may be your best option if you are unsure about your LMP.
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⚠️ Medical Disclaimer: This calculator provides general estimates for informational purposes only. Gestational age and due dates should be confirmed by a healthcare provider through clinical evaluation and ultrasound. This tool is not a substitute for professional medical advice, diagnosis, or treatment.
