Calculator guide
Pregnancy Calculator helps you explore the stated health question. Start with the labelled inputs, then review the method, worked example and limitations before using a result.
Formula or method
Estimate gestational age and due-date milestones from the selected pregnancy dating information; last-period dating convention counts from the period rather than conception.
How to use this calculator
- Enter the last menstrual period date and the cycle length.
- Use the estimated timeline as a calendar aid, not a clinical dating assessment.
Worked example
January 29 is 28 days after January 1, so last-period dating gives 4 weeks on January 29 for a January 1 start.
Understanding the result
Compare the output with the pregnancy calculator worked example using exactly the same inputs. A different assumption or rounding convention can produce a different displayed result; the output does not establish personal or professional suitability.
Limitations and assumptions
- Clinical dating can differ from calendar dating. Do not use milestone estimates to decide whether urgent symptoms need medical care.
- The worked example demonstrates the stated assumptions, not a recommendation about your personal circumstances.
Frequently asked questions
Which inputs should I check first?
Follow the Pregnancy Calculator input instructions above. Check each measurement, date, selection or expression before comparing results.
Why might my result differ from another tool?
Compare the other tool's pregnancy calculator method, input units, rounding and assumptions. A matching title does not guarantee that both tools answer the same question.
Does a linked reference certify this result?
No. A reference can explain a formula or provide background for Pregnancy Calculator, but it does not endorse this website, validate personal inputs or establish professional suitability.
Sources
Educational and planning information only. Sources are attributed background or formula references, not endorsements. Verify consequential decisions with an appropriate qualified professional.