How this calculator works
The standard due date estimate adds 280 days, or 40 weeks, to the first day of the last menstrual period. This is a common medical convention for estimating a due date in uncomplicated pregnancies.
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Pregnancy Due Date Calculator
Free pregnancy due date calculator based on last menstrual period. Estimate expected due date and pregnancy timeline using a simple standard method.
Instant result
Estimated due date
October 8, 2026
Calculator results are provided for planning and educational purposes. For taxes, legal decisions, lending, or medical advice, verify the numbers with an official source or qualified professional.
About this calculator
This pregnancy due date calculator estimates an expected due date using the first day of your last menstrual period, which is the most common starting point for basic due date estimation. It is a convenient tool for an early timeline before you receive individualized dating from a healthcare provider.
How to use it
- Select the first day of your last menstrual period.
- Review the estimated due date generated by the calculator.
- Use the date as a general planning reference for appointments and milestones.
- Confirm dating with your OB-GYN or midwife, especially if cycle length varies or ultrasound findings differ.
Example
If your last menstrual period began on January 1, the calculator adds 280 days to estimate an expected due date in early October.
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Frequently asked questions
Is the due date exact?
No. It is an estimate. Only a small percentage of babies arrive on the exact due date, and your provider may adjust dating based on cycle length or ultrasound measurements.
Can I use this with irregular periods?
You can use it for a rough estimate, but irregular cycles can make the result less reliable. A clinician may provide a more accurate due date after evaluation.
Does this replace medical advice?
No. This tool is for general planning only and should not replace prenatal care or professional medical guidance.