Conception Calculator
Estimate your conception date based on due date or last menstrual period
Calculate Your Conception Date
Important Notice
Conception dates are estimates only. Actual conception could occur up to 5 days before or 1 day after the calculated date due to sperm survival and the fertile window.
Medical Disclaimer
This calculator provides estimates for educational purposes only. For accurate pregnancy dating, please consult with your healthcare provider and consider ultrasound dating.
How It Works
Due Date Method
Subtracts 266 days from your due date
LMP Method
Calculates ovulation based on cycle length
Fertile Window
Shows the 6-day window when conception was possible
Calculation Formulas
Due Date Method
Due Date - 266 days = Conception
LMP Method
LMP + (Cycle Length - 14) = Conception
Accuracy Information
Estimates are within ±5 days for regular cycles
Ultrasound dating is most accurate (±1-2 days)
Works best with cycles between 21-35 days
Consult healthcare provider for medical decisions
Understanding Conception Dating
What is Conception?
Conception occurs when a sperm successfully fertilizes an egg, typically in the fallopian tubes. This usually happens within 24 hours of ovulation, when the egg is released from the ovary.
Fertile Window
- •Sperm can survive up to 5 days in the female reproductive tract
- •Eggs remain viable for 12-24 hours after ovulation
- •Fertile window spans approximately 6 days total
Calculation Methods
Due Date Method
Based on the standard 280-day pregnancy (40 weeks from LMP), conception typically occurs 266 days before the due date.
LMP Method
Uses your cycle length to estimate ovulation day. Ovulation typically occurs 14 days before the next expected period.
Factors Affecting Accuracy
Factors that Improve Accuracy:
- • Regular menstrual cycles
- • Accurate LMP date
- • Known ovulation date
- • Professional ultrasound dating
Factors that Reduce Accuracy:
- • Irregular cycles
- • PCOS or other hormonal conditions
- • Recent contraceptive use
- • Breastfeeding