Plain-language meaning
Many due date calculators estimate the due date by adding about 280 days to the LMP, with cycle-length adjustment if supported.
Example
An LMP of January 1 with a 28-day cycle gives an estimated due date around October 8.
Limitations
Ovulation timing and cycle irregularity can make LMP estimates differ from clinical dating.
How this term affects your result
Last Menstrual Period affects the result through the units, time period, rate, threshold or method used by the related calculator. Read it together with the page's formula and assumptions before comparing results across tools or sources.
What to check
- Use the same unit system, currency and time period as the related calculator.
- For regulated, health, tax, finance, safety or live-data topics, check the primary source named on the related page.
- If the term is used as a threshold, rate or category boundary, confirm the exact definition before relying on the estimate.
FAQ
Is Last Menstrual Period defined the same way everywhere?
Not always. Some terms are mathematical and stable, while others vary by country, institution, industry, product or data source.
Why link glossary terms to calculators?
Calculator users often need the term at the moment they interpret a result. Linking the definition to the calculator reduces ambiguity.