Conception Date Estimate
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Rough conception date from LMP (ovulation ≈ day 14) or back-calculated from due date.
Rates last reviewed: July 2026
Dating method
Estimated conception
2026-01-24
~14 days after LMP 2026-01-10
- Conception date (estimate)
- 2026-01-24
Related calculators
Estimating conception date
Conception usually occurs around ovulation — roughly 14 days after the start of the last menstrual period in a 28-day cycle. From LMP, this calculator adds 14 days. From a known due date, it subtracts 266 days (280-day gestation minus the 14-day LMP offset).
Actual fertilization timing varies with cycle length, sperm survival, and IVF protocols. Ultrasound dating in early pregnancy is far more reliable than backward math from LMP alone.
Example: LMP January 10, 2026 → estimated conception around January 24, 2026. EDD October 17, 2026 → same conception estimate via the 266-day back-calculation.
Official sources
Rates and formulas in this calculator are based on the documentation below. Platforms change fees — confirm current numbers before pricing or payouts.
Common questions
How accurate is the 14-day rule?
It assumes a 28-day cycle with ovulation on day 14. Longer or irregular cycles shift ovulation — ask your clinician for personalized dating.
Does this work for IVF?
IVF uses the embryo transfer date and embryo age — use our IVF due date calculator instead.