Loading calculator…
What this calculator does
Estimate a due date from the first day of the last menstrual period.
How to use this calculator
- Enter the relevant start date.
- Review the calculation assumptions before using the result.
- The date is a planning estimate, not a guarantee.
How to calculate
Enter the values requested by the pregnancy due date calculator.
Worked example
With the example values shown above, the estimated due date is 2026-10-08.
Understanding your result
The date is a planning estimate, not a guarantee.
- Cycle length and clinical dating can change it.
- Double-check values and units before calculating.
This calculator is educational and is not financial or medical advice.
Frequently asked questions
What does this pregnancy due date calculator do?
Estimate a due date from the first day of the last menstrual period.
How do I use this pregnancy due date calculator?
Enter the relevant start date.
What does the result mean?
The date is a planning estimate, not a guarantee.
What should I check before relying on it?
Cycle length and clinical dating can change it.
How accurate is a due date based on the last period?
It's a widely used estimate, but only about 5% of babies are born on their exact due date — actual delivery can happen anywhere in a range of a few weeks around it.
Why does cycle length matter for the estimate?
The standard 280-day estimate assumes a 28-day cycle with ovulation around day 14. A longer or shorter cycle shifts the likely ovulation and conception date, which shifts the due date accordingly.