Pregnancy Due Date Calculator
Estimate due date and gestational week from LMP or conception while preserving clinician dating authority. Sensitive inputs stay in your browser.
Uses 280 days from LMP, adjusted by +0 days for the entered cycle length.
Context matters.
- An early ultrasound and the clinician's documented best obstetric estimate can replace an LMP calculation. Do not redetermine a due date from later scans without clinical guidance.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Estimate due date and gestational week from LMP or conception while preserving clinician dating authority. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Known date, Known date, Typical cycle length (days) and Pregnancy week on supplied in the form.
- Apply the scope. It applies the Pregnancy dating education — clinician-documented best obstetric estimate controls reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
Uses 280 days from LMP, adjusted by +0 days for the entered cycle length.
- Estimated due dateMar 30, 2027
Calculation purpose: Estimate due date and gestational week from LMP or conception while preserving clinician dating authority. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-20 · Next review due 2027-02-20. The source panel below contains the linked evidence.
What to know before using the result.
How is a due date estimated from the last menstrual period?
The common calendar estimate is 280 days from the first day of the last menstrual period.
How is a conception-date estimate different?
A conception-date estimate uses approximately 266 days, reflecting the conventional two-week gestational-age offset.
Which due date should be used for care decisions?
The clinician-documented best obstetric estimate controls, especially when ultrasound or assisted-reproduction dating is available.