Conception Date Calculator
Estimate conception date based on due date or last menstrual period
About this calculator
A conception date calculator helps estimate when conception likely occurred based on your due date or last menstrual period (LMP). This tool is valuable for expectant parents who want to understand their pregnancy timeline, track fetal development milestones, or determine paternity windows. The calculator uses standard pregnancy duration of 280 days from LMP or 266 days from conception to provide accurate estimates for family planning and medical appointments.
How to use
Enter either your baby's due date or the first day of your last menstrual period into the calculator. Select which information you're providing using the input options. Click calculate to instantly receive your estimated conception date range, which typically spans a few days to account for natural variations in ovulation timing.
Frequently asked questions
How accurate is a conception date calculator?
Conception calculators provide estimates within 3-5 days of the actual conception date, as ovulation timing varies between individuals and cycles.
Can I use this if I have irregular periods?
The calculator works best with regular cycles. For irregular periods, consult your healthcare provider for more accurate dating methods.
What's the difference between conception date and due date?
Conception occurs about 14 days after your last period, while due date is calculated 280 days from your LMP.