HEALTH REFERENCES WITH CLEAR LIMITS

Pregnancy Due Date Calculator

Estimate a due date by adding 280 days to the first day of the last menstrual period.

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Your result

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Enter your values and select Calculate. Your result stays on this device.

How it works

Estimated due date = first day of the last menstrual period + 280 days.

Assumptions

This convention assumes a regular 28-day cycle. An early ultrasound or clinician may change the estimated date.

Use case

pregnancy calculator: a clear planning check

Estimate a due date by adding 280 days to the first day of the last menstrual period. The stated formula, assumptions, and result limits remain visible so the calculation can be checked in context.

Use a clear pregnancy calculator scenario with values you can verify before relying on the result.

Build a reliable scenario

How to use and verify your Pregnancy Due Date Calculator result

Pregnancy Due Date Calculator helps you check a specific health & family question with figures that apply to you. Estimate a due date by adding 280 days to the first day of the last menstrual period. Estimate a due date by adding 280 days to the first day of the last menstrual period. The stated formula, assumptions, and result limits remain visible so the calculation can be checked in context. Use a clear pregnancy calculator scenario with values you can verify before relying on the result. The page keeps the method and limits visible so the result can be understood, compared, and checked instead of treated as an unexplained answer.

Before calculating

Prepare First day of last menstrual period and Days to add. Match each input to the document, measurement, or current source you are using. Keep units, dates, currency, and time periods consistent.

What changes the result?

The stated method is: Estimated due date = first day of the last menstrual period + 280 days. Change one assumption at a time to see which input drives the result, then compare scenarios on the same basis.

When checking the answer

This convention assumes a regular 28-day cycle. An early ultrasound or clinician may change the estimated date. This is an estimate, not a diagnosis or confirmed delivery date. Contact a clinician for medical questions, bleeding, pain, or urgent symptoms.

Quick verification checklist

• Confirm the date and unit of every input.
• Replace defaults with values that match your case.
• Compare the answer with a second scenario.
• Use the official source for regulated or high-impact decisions.

Source and update

Last reviewed: 2026-08-10

ACOG — methods for estimating the due date

Frequently asked questions

Is Pregnancy Due Date Calculator free to use?

Yes. This calculator runs in your browser and does not require an account.

Is the result guaranteed?