Why is conception different from LMP?
Medical professionals date from LMP because exact conception is often uncertain. Ovulation occurs ~2 weeks after LMP.
Health Fitness
Conception Date Calculator
Calculate conception date with your details.
Personalized estimate
Use realistic inputs for the most useful results.
What this calculator does
Conception date is when sperm fertilizes egg, typically 14 days before next period. Different from last menstrual period (LMP) used for pregnancy dating.
How it works
Ovulation = LMP + (Cycle Length - 14 days). Fertile window is 5 days before through 1 day after ovulation.
Formula
Ovulation Date = LMP + (Cycle Length - 14). Standard cycle is 28 days.
Tips for using this calculator
- Track cycle for 2-3 months before using calculator
- Conception dates are estimates—ultrasound is most accurate
- Adjust for non-standard cycle lengths
- Ovulation can vary due to stress or illness
- Consider ovulation predictor kits for precision
Frequently asked questions
What if my cycle isn't 28 days?
Enter actual cycle length. 30-day cycle: ovulation around day 16. 26-day: around day 12.
Can I conceive outside fertile window?
The window has highest probability (20-30% per cycle), but sperm can survive 5 days.