Our conception date calculator estimates when conception likely occurred by working backward from your due date. Conception typically happens around ovulation — about 14 days after the first day of your last menstrual period for a standard 28-day cycle.
The calculator also estimates your fertile window, approximate implantation date (6-12 days after ovulation), and when you can expect a positive pregnancy test. This reverse calculation is useful for dating a pregnancy when the exact LMP is unknown.
All calculations are performed locally in your browser. No data is stored or transmitted.
Estimate when conception likely occurred