Reverse Due Date Calculator
Calculate conception date, intercourse timing, and pregnancy planning from any known date
Calculate Conception and Timing
Select the date you want to work backwards from
How to Use This Calculator
1. Select what date you know: Choose whether you have a due date, birthday, conception date, or intercourse date.
2. Enter the date: Input the known date using the date picker.
3. Advanced options: Adjust pregnancy length if you know the exact duration (default is 40 weeks).
4. View results: See the calculated conception date, fertile window, and other relevant dates.
Example Calculation
Example: Baby Born July 15, 2024
Birthday: July 15, 2024
Conception Date: ~October 22, 2023
Fertile Window: October 17-24, 2023
Calculation: July 15 - 280 days = October 22
Planning Example
Desired Due Date: December 25, 2024
Best Conception Time: ~March 31, 2024
Intercourse Window: March 26 - April 2, 2024
Key Information
Standard Assumptions
• Pregnancy length: 40 weeks (280 days)
• Menstrual cycle: 28 days
• Ovulation: Day 14 of cycle
• Fertility window: 6-7 days
Accuracy Note
These are estimates based on average values. Individual pregnancies can vary by ±2 weeks from calculated dates.
Pregnancy Timeline
Conception
Fertilization occurs
Implantation (+7 days)
Embryo attaches to uterus
First Ultrasound (+11-13 weeks)
CRL measurement, heartbeat
Delivery (+40 weeks)
Expected birth date
Understanding Reverse Due Date Calculation
What is Reverse Due Date Calculation?
Reverse due date calculation works backwards from a known date (due date, birthday, etc.) to determine when conception occurred and the optimal timing for intercourse. This is useful for pregnancy planning or understanding conception timing.
Uses and Applications
- •Planning pregnancy for specific timing
- •Understanding when conception occurred
- •Determining fertile window timing
- •Educational and curiosity purposes
Calculation Method
Conception Date = Due Date - 280 days
Fertile Window = Conception Date ± 5-7 days
Important Considerations
Variability: Actual conception can vary ±2 weeks from calculations
Cycle Length: Assumes 28-day menstrual cycle
Individual Factors: Ovulation timing varies between women
Medical Input: Consult healthcare providers for planning
⚠️ Medical Disclaimer
This calculator provides estimates based on standard pregnancy calculations and should not be used as the sole method for pregnancy planning or medical decisions. Conception timing can vary significantly due to individual factors including cycle irregularities, ovulation timing, and other health factors. Always consult with a healthcare provider for personalized medical advice and pregnancy planning guidance.