Conception Calculator
Pick the starting point you have. We'll estimate your likely conception date and fertile window.
How we estimate conception
Conception usually happens within a 5-day fertile window that ends on the day of ovulation, typically about 14 days before your next period. To project forward from there, use our Due Date Calculator. For a 28-day cycle that's day 14. We adjust for longer or shorter cycles so the estimate makes sense for you.
For ultrasound dating, we work backward from the gestational age the scan measured. For IVF, conception is the day the egg was fertilized: 5 days before a blastocyst transfer, 3 days before a day-3 transfer. After birth, the Baby Percentile Calculator shows where your baby lands on WHO growth curves.
Read more: Due Date vs Conception Date: How They Differ.