Gestational Age Calculator
Calculate the gestational age based on the first day of the last menstrual period (LMP) or the conception date. Provides current gestational age in weeks and days, expected due date, and trimester information.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Gestational Age Calculator
This calculator estimates your current gestational age, expected due date, and trimester based on your last menstrual period (LMP).
- Enter LMP Date – Input the first day of your last menstrual period. This is required.
- Enter Conception Date (Optional) – If known, you can add the conception date for reference (not used in calculations).
- Current Date – This is automatically set to today’s date. You can change it if needed.
- Click “Calculate” – The results will show:
- Gestational Age – in weeks and days (calculated as difference between current date and LMP).
- Expected Due Date – LMP + 280 days (40 weeks).
- Trimester – Based on gestational age (First: 0–12 weeks, Second: 13–26 weeks, Third: 27+ weeks).
Note: All dates must be valid. The current date cannot be before the LMP date. The calculator uses the standard 280-day pregnancy model.
Previous Results
| Result | Inputs | Date |
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Frequently Asked Questions
Gestational age is the age of a pregnancy measured from the first day of the last menstrual period (LMP) to the current date, usually expressed in weeks and days.
The due date is calculated by adding 280 days (40 weeks) to the first day of the last menstrual period. This is known as Naegele's rule.
Yes, you can optionally enter the conception date. If provided, the calculator will use it to cross-check, but the primary calculation is based on LMP.
