Dating audit
See exactly how this EDD was derived. No hidden date shift, cycle assumption or embryo-age adjustment.
OneFreePlace · Tool #143
One due-date workspace for LMP, conception, IVF and ultrasound.
Calculate an estimated due date from the information you actually have, then track gestational age on any date, inspect trimester and term milestones, reverse-calculate estimated dates, and compare a second EDD without silently deciding which date should replace the clinical record.
✓ LMP + cycle adjustment✓ Conception / ovulation date
✓ IVF day-3 / day-5 / custom embryo age✓ Ultrasound GA on scan date
✓ Gestational age + term timeline
Pregnancy Due Date Calculator
EDD · gestational age · IVF · ultrasound · trimester/term timeline · comparison
Dating method
Choose the source that best matches the information you have.
Last menstrual periodStandard EDD is 280 days from LMP; cycle adjustment shifts by cycle length − 28 days.
Gestational age “as of”Use today or any other calendar date.
Optional second EDD comparisonUseful for comparing LMP, ultrasound or clinic dates. The tool reports the difference but does not make a redating decision.
LMP dating conventionally uses 280 days from the first day of the last menstrual period. The optional cycle-length adjustment shifts the estimate relative to a 28-day cycle.
Estimated due date
Calculating—
estimated due date · 40w0d
Enter a valid dating source.
Gestational age on as-of date—completed weeks + days
Time to / from EDD—relative to 40w0d
EDD-implied gestational day 0—EDD minus 280 days; may differ from entered LMP after cycle adjustment
Estimated conception date—EDD minus 266 days
Trimester—ACOG trimester boundaries
Term category—based on completed gestational weeks
Pregnancy timeline—
Estimated dateYour clinician’s documented obstetric EDD should guide care when it differs from a consumer calculator.
EDD comparison
If you enter a second due date, the tool reports the difference in calendar days. It intentionally does not automatically choose or replace the clinically documented date.
Pregnancy milestone calendar
Calendar anchors derived from the selected EDD. These are gestational dates—not appointment recommendations.
Term timeline
Modern obstetric terminology separates “term” into early, full, late and postterm ranges rather than treating every week after 37 as identical.
Method context
Last menstrual periodConventional EDD is 280 days from LMP and assumes a 28-day cycle with ovulation around day 14; cycle variation can shift the estimate.
Calendar estimateFirst-trimester ultrasoundACOG identifies first-trimester ultrasound, through 13w6d, as the most accurate ultrasound method to establish or confirm gestational age.
Clinical datingAssisted reproductionACOG recommends ART-derived gestational age using embryo age and transfer date; day-5 transfer maps to transfer +261 days and day-3 to +263 days.
ART-specificConception dateWhen genuinely known, conception-to-EDD arithmetic is 266 days. In spontaneous conception, the exact fertilization date is often uncertain.
Known-date estimateImportant limits
Do not self-redate a pregnancy from this toolACOG uses gestational-age-specific ultrasound discrepancy thresholds and clinical judgment. Your documented EDD should be changed by the treating team, not by a web calculator.
Clinical decisionCycle adjustment is still an estimateA longer or shorter cycle does not prove ovulation occurred exactly that many days later or earlier.
AssumptionSymptoms override calendar mathUrgent pregnancy symptoms, labor concerns, bleeding, reduced fetal movement or other problems require clinical guidance regardless of the calculated week.
Seek carei
Use the clinically documented EDD for medical decisions.This calculator is designed for transparent date arithmetic and planning. ACOG recommends determining and documenting the EDD as soon as LMP and/or the first accurate ultrasound are available, with later changes reserved for specific circumstances.