Gestational Age Calculator
Calculate gestational age from your last menstrual period, due date, or ultrasound. Track your pregnancy progress and fetal development milestones.
Calculate Gestational Age
First day of your last menstrual period
Pregnancy Progress
How to Use This Calculator
Calculation Methods
- • LMP Method: Most common, based on last menstrual period
- • Due Date Method: Calculate from known due date
- • Ultrasound Method: Most accurate, based on ultrasound measurements
Important Notes
- • Gestational age is calculated from LMP, not conception
- • Ultrasound dating is most accurate in first trimester
- • Always consult your healthcare provider for medical advice
- • Due dates are estimates, not guarantees
Frequently Asked Questions
What is gestational age?
Gestational age is the age of the pregnancy calculated from the first day of your last menstrual period (LMP). It's typically about 2 weeks ahead of the actual conception date.
Which calculation method is most accurate?
Ultrasound dating in the first trimester is the most accurate method. LMP dating assumes a 28-day cycle and ovulation on day 14, which may not be accurate for all women.
Why is my due date different from what my doctor said?
Healthcare providers may adjust due dates based on ultrasound measurements, especially if there's a significant difference from LMP dating. Always follow your doctor's recommended due date.
What if I don't know my LMP date?
If you don't know your LMP date, use the ultrasound method if you have ultrasound results, or consult your healthcare provider for the most accurate dating method.
How the Gestational Age calculator works
This free gestational age calculator runs entirely in your browser using standard mathematical formulas. Enter your figures, tap Calculate, and results update instantly — no signup required.
Figures are estimates for general information. Always verify important decisions with a qualified professional where relevant.
- Input your values using the fields above (numeric keypad on mobile).
- Results use precise floating-point arithmetic rounded for display.
- Refresh or change inputs and recalculate anytime.
Worked example
- Choose typical values for a common gestational age scenario.
- Enter those values in the calculator fields above.
- Tap Calculate and compare the on-screen result with the expected formula outcome.
- Adjust one input at a time to see how the result changes.
Frequently Asked Questions
Is the Gestational Age calculator free?
How accurate is this gestational age calculator?
Does it work on mobile?
Are my numbers stored?
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