What is a pregnancy?
Pregnancy dating commonly starts on the first day of the last menstrual period (LMP), not the date of conception. This calculator estimates gestational age and a 40-week due date using that date. Cycle variation and ultrasound dating can change the estimate; confirm pregnancy care with a qualified clinician.
Formula and calculation method
Estimated due date = first day of LMP + 280 days. Gestational age = elapsed days since LMP, expressed in weeks and days.
The result is only as reliable as the inputs and assumptions. This tool is educational and does not replace professional financial, medical, legal or academic advice.
How to use this calculator
- Enter the values requested in the calculator.
- Review the result panel; it updates when an input changes.
- Change one assumption at a time to compare scenarios.
- Check the formula and limitations before acting on the estimate.
Frequently asked questions
Is this pregnancy calculator free?
Yes. You can use this calculator in your browser without creating an account.
How accurate is the result?
It applies the displayed formula to the values you provide. Real-world outcomes can differ because of fees, changing rates, individual circumstances or rules not represented in this estimate.
Are my inputs stored?
No. The calculation runs locally in your browser and the values are not submitted to FastSEOHub.