Fitness and health calculators
Due Date Estimate
Estimate a due date from last menstrual period and average cycle length.
Calculator & Result
For general education only, not diagnosis or medical advice. Personal needs vary; consult a qualified health professional.
How to Use This Calculator
- Review the default values and replace them with your own First day of last menstrual period, Average cycle length (days).
- Keep units, dates, percentages, and time periods consistent with the labels shown beside each field.
- Read the primary result first, then compare the supporting results and assumptions below it.
- Change one assumption at a time to see how sensitive the estimate is before using it in a real decision.
Detailed Breakdown
The estimate adds 280 days adjusted by the difference between the entered cycle length and a 28-day reference cycle. Only a clinician can assess pregnancy dating for care.
This page reports Estimated due date, Estimated gestational duration. The first value is the headline estimate; the other values help you understand the calculation rather than acting as separate guarantees. Use the result as a comparison starting point, and test a conservative and an optimistic input set when the decision has financial, health, safety, or construction consequences.
Examples
Using the sample inputs (First day of last menstrual period: 2026-08-01; Average cycle length (days): 28), the estimated due date is May 8, 2027. Change the inputs above to try your own values.
Assumptions and Limitations
- The estimate adds 280 days adjusted by the difference between the entered cycle length and a 28-day reference cycle. Only a clinician can assess pregnancy dating for care.
- Small changes in the inputs can materially change the output. Rounded values, missing fees, unusual cases, and local rules may not be represented.
- For general education only, not diagnosis or medical advice. Personal needs vary; consult a qualified health professional.
- Verify important results against an authoritative source or qualified professional before acting.
Frequently Asked Questions
What does the Due Date Estimate calculate?
Estimate a due date from last menstrual period and average cycle length. The estimate adds 280 days adjusted by the difference between the entered cycle length and a 28-day reference cycle. Only a clinician can assess pregnancy dating for care.
How should I use the result?
Use it to compare scenarios and identify the inputs that matter most. Recalculate after changing assumptions, and do not treat an estimate as a quote, diagnosis, approval, or guarantee.
Why might my real-world result be different?
Actual results can differ because of fees, taxes, rounding, timing, eligibility rules, measurement error, market changes, or local requirements that are not included in this simplified model.
Can I rely on this estimate as a final decision?
No. Review the displayed assumptions and verify important results with an appropriate professional or authoritative source before acting.
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