Pregnancy Conception Calculator
Estimate your conception date from due date or last menstrual period.
Pregnancy Conception Calculator
Estimate your conception date from due date or last menstrual period.
Pregnancy Due Date — Naegele's Rule
ℹ️ Only 5% of babies are born on their exact due date. Dates are estimates only.
Disclaimer
Results provided by this calculator are for informational and educational purposes only. They are based on the values you enter and standard formulas, and should not be considered financial, medical, legal, or professional advice. Always consult a qualified professional before making important decisions based on these results. Roughtools makes no warranties regarding the accuracy or completeness of these calculations for your specific situation.
Frequently Asked Questions
Pro Tips
Only about 5% of babies are born on their due date — the Naegele's Rule date is the midpoint of a 5-week window. Don't over-plan for the exact date.
Early ultrasound (6-10 weeks) is more accurate for dating than last menstrual period if your cycles are irregular. Your OB may adjust your due date based on ultrasound.
Gestational age in weeks is counted from LMP, not conception. "6 weeks pregnant" means 6 weeks since your last period, which is only 4 weeks since likely conception.
Track your symptoms week by week using the trimester milestones. Many pregnancy apps let you export a report — useful to share with your healthcare provider.
When to Use This Calculator
Calculate your due date to plan maternity leave timing, financial preparation, and childcare arrangements.
Calculate your estimated due date in advance so you can ask the right questions at your first OB appointment.
Know your due date to schedule the baby shower at the right time — typically 4–6 weeks before delivery.
Share your due date with family and friends as a planning tool, while reminding them only 5% of babies arrive on that date.
Parents of multiple children often plan birth timing around school enrollment cutoffs — use the due date to estimate.
About the Pregnancy Conception Calculator
The Pregnancy Conception Calculator works backwards from your estimated due date or last menstrual period to identify the most likely conception window. It displays the estimated fertilization date, the ovulation window, and a calendar view. Since conception can only occur around ovulation, the window is typically 5–6 days long.
How to Use the Pregnancy Conception Calculator
- 1
Select whether to calculate from due date or last menstrual period.
- 2
Enter the date.
- 3
Click Calculate to see the estimated conception window.
- 4
Review the calendar highlighting the ovulation and fertile period.
Related Calculators
View all →Conception Calculator
Estimate your most likely conception date based on your due date or LMP.
Due Date Calculator
Calculate pregnancy due date from last menstrual period or conception date.
Pregnancy Calculator
Calculate pregnancy week, trimester, and key milestone dates.
Ovulation Calculator
Calculate ovulation window and fertile days from your cycle length.
Your input is processed locally in your browser and is never stored, transmitted, or shared with any server. See our Privacy Policy.