Pregnancy Conception Date Calculator to Estimate...
Estimate your likely conception date from your due date or last menstrual period. Understand ovulation timing, fertile windows, and how conception date relates to...
Estimating Conception Date
Conception typically occurs about 14 days after the first day of the last menstrual period (LMP) — during ovulation. Knowing the approximate conception date helps establish paternity timing, explain early symptom onset, and clarify discrepancies between LMP-based and ultrasound-based dating.
🗓️ Conception Date Calculator
Free calculator for instant results.
📐 Formula
Conception Date ≈ LMP + 14 days
Or work backward from due date: Conception ≈ EDD − 266 days. The fertile window spans Day 10–17 of a 28-day cycle. Sperm can survive 3–5 days; egg is viable ~24 hours.
📝 Worked Example
LMP = January 1, 2026:
Conception window: Jan 12–18 (peak: Jan 15)
EDD = October 8, 2026
Working backward: Oct 8 − 266 days = January 15, 2026
📝 How to Use
❓ FAQ
Can conception happen outside the fertile window?
Rarely, but possible. Sperm survive 3–5 days, so intercourse before ovulation can still result in conception. Ovulation can also occasionally occur at irregular times.
How accurate is conception date estimation?
Even with perfect LMP data, conception date estimates have ±7 day uncertainty. Early ultrasound (8–10 weeks) provides independent confirmation.
Veer Kumavat
Founder & AuthorVeer is a 14-year-old student from Nashik, Maharashtra, who built SciFi Calculators to help students worldwide master STEM subjects. He is passionate about making complex science and math problems accessible through intuitive digital tools.