Pregnancy Due Date Calculator

Estimate a due date from the recorded LMP, show the cycle-length adjustment, and calculate elapsed time for a chosen date. The calculator keeps estimated due date = LMP + 280 days + (usual cycle length - 28 days) visible so the selected inputs and resulting estimated due date can be checked together.

Add source values for pregnancy due date

The question answered by pregnancy due date

Estimate a due date from the recorded LMP, show the cycle-length adjustment, and calculate elapsed time for a chosen date.

This page limits estimated due date to the fields and cycle-adjusted last-menstrual-period dating relationship shown, without filling gaps from personal or clinical context.

How each field enters estimated due date

First day of last menstrual period: Enter first day of last menstrual period in the unit shown beside the field; the pregnancy due date illustration uses 2026-07-01. Digits copied in a different unit change estimated due date under cycle-adjusted last-menstrual-period dating.
Usual cycle length: For this pregnancy due date case, usual cycle length starts at 28 days. Record whether it was measured, selected, or copied before using estimated due date from estimated due date = LMP + 280 days + (usual cycle length - 28 days). Under cycle-adjusted last-menstrual-period dating, the accepted range for usual cycle length runs from 20 through 45.
As-of date: For pregnancy due date, the worked as-of date is 2026-07-15. Preserve the unit shown beside the field and its measurement source because this field supplies a distinct term in cycle-adjusted last-menstrual-period dating.

The pregnancy due date inputs must share a compatible source and time boundary, because otherwise valid arithmetic can describe a nonexistent case.

Arithmetic behind pregnancy due date

estimated due date = LMP + 280 days + (usual cycle length - 28 days)

Under cycle-adjusted last-menstrual-period dating, the result panel reports estimated due date, elapsed gestational time, time until estimated due date. Match each symbol or operation in estimated due date = LMP + 280 days + (usual cycle length - 28 days) to the labeled first day of last menstrual period, usual cycle length, as-of date fields before substituting numbers.

For pregnancy due date, check which date starts estimated due date = LMP + 280 days + (usual cycle length - 28 days) and whether the endpoint is included; reversing two dates changes the timeline's sign or direction.

The surrounding record may also call for pregnancy due date by ivf and pregnancy weight gain.

Tracing the displayed pregnancy due date case

The displayed case begins with First day of last menstrual period = 2026-07-01, Usual cycle length = 28 days, As-of date = 2026-07-15.

Using those defaults, the calculator reports Estimated due date = April 7, 2027; Time until estimated due date = 266 days. This fixed pregnancy due date case checks estimated due date = LMP + 280 days + (usual cycle length - 28 days) after code, browser, or formatting changes.

Test estimated due date by changing a single pregnancy due date assumption before altering the rest of the setup.

What the cycle adjustment assumes

For pregnancy due date, the conventional LMP estimate is 280 days for a 28-day cycle. For pregnancy due date, adding the difference between the entered cycle length and 28 days assumes ovulation shifts by the same amount, which may not be true.

For pregnancy due date, irregular cycles, uncertain bleeding dates, assisted reproduction, and ultrasound findings require different dating evidence. For pregnancy due date, once clinical dating is established, use the documented obstetric due date.

Interpreting estimated due date in context

For pregnancy due date under cycle-adjusted last-menstrual-period dating, family-planning dates and estimates describe a calendar model, not a biological certainty; cycle variation, pregnancy history, testing, symptoms, and clinical findings can change interpretation.

Calendar outputs from pregnancy due date under cycle-adjusted last-menstrual-period dating should retain the source dates, not only an elapsed-day or projected-date result.

Testing the stability of estimated due date

For pregnancy due date, first vary first day of last menstrual period within a defensible range while holding the other entries fixed under cycle-adjusted last-menstrual-period dating. Explain the direction of the new estimated due date from estimated due date = LMP + 280 days + (usual cycle length - 28 days), rather than judging it only by familiarity.

Repeat the pregnancy due date exercise with as-of date under estimated due date = LMP + 280 days + (usual cycle length - 28 days). If both changes alter the conclusion, report alternative cycle-adjusted last-menstrual-period dating cases instead of presenting one scenario as exact.

When a plausible estimated due date can be wrong

Check first day of last menstrual period, usual cycle length, as-of date against their labels in estimated due date = LMP + 280 days + (usual cycle length - 28 days). A transposed value can remain numerically valid while describing a different cycle-adjusted last-menstrual-period dating setup.

For pregnancy due date under cycle-adjusted last-menstrual-period dating, do not substitute zero for missing data, reuse a rounded intermediate as the original measurement, or combine time boundaries.

Keeping a reproducible pregnancy due date record

When recording pregnancy due date from cycle-adjusted last-menstrual-period dating, record the date source and whether a value was observed, estimated, or projected before comparing family-planning timelines.

Store first day of last menstrual period, usual cycle length, as-of date, their units and dates, the equation estimated due date = LMP + 280 days + (usual cycle length - 28 days), and the unrounded estimated due date, elapsed gestational time, time until estimated due date values. Note pregnancy due date exclusions or selected rates explicitly so another reader can reconstruct the cycle-adjusted last-menstrual-period dating result.

Checking estimated due date before reuse

How much should estimated due date be rounded?

Preserve the exact source dates and the cycle-adjusted last-menstrual-period dating calendar rule. Report estimated due date to the day; decimal precision does not apply to estimated due date = LMP + 280 days + (usual cycle length - 28 days).

Why could another pregnancy due date tool disagree?

Another tool may use a different cycle-adjusted last-menstrual-period dating convention, unit, date boundary, reference population, or rounding rule. Compare the pregnancy due date equations and field definitions under cycle-adjusted last-menstrual-period dating before deciding that either result is erroneous.