Conception Date Calculator
Estimate your likely conception date based on your last menstrual period or due date. Useful for understanding pregnancy timeline and gestational milestones.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Conception Date Calculator | — | Conception ≈ LMP + 14 days (average cycle) | date estimate |
Step-by-Step Examples
LMP date: March 1, 2026. Standard 28-day cycle.
- Ovulation typically occurs 14 days before next period
- Conception ≈ March 1 + 14 days = March 15, 2026
- Due date ≈ conception + 266 days = December 5, 2026
LMP date: March 1, 2026. Cycle length: 32 days.
- Ovulation day = cycle length - 14 = 32-14 = 18
- Conception ≈ March 1 + 18 days = March 19, 2026
- Longer cycles shift ovulation later in the cycle
Known due date: December 10, 2026.
- Conception ≈ due date - 266 days
- December 10, 2026 minus 266 days ≈ March 19, 2026
Real-World Applications
Common Mistakes to Avoid
Sperm can survive several days, and ovulation timing varies — actual conception could occur within a window of several days around the estimated date.
Women with irregular or longer/shorter cycles than 28 days will have ovulation (and thus likely conception) at different relative timing — input your actual average cycle length if known.
Medical convention counts pregnancy weeks from LMP, not from conception — so 'week 4 of pregnancy' is actually only about 2 weeks post-conception, which often surprises new parents.