Conception Calculator
Estimate your conception date and fertile window from the first day of your last menstrual period.
- Free to use
- No registration required
- Works on all devices
- Last updated
- 13-09-2026
Your result
15-06-2026
Estimated conception date
AI explanation
Formula
Estimated conception = last period date + 14 days, assuming a standard 28-day cycleWorked example
LMP 2026-01-01
| Field | Value |
|---|---|
| First day of last menstrual period | 01-01-2026 |
| Estimated conception date | 15-01-2026 |
Assumptions
- Assumes ovulation (and conception) occurs around day 14 of a standard 28-day cycle.
- The conception window spans a few days either side of the estimated ovulation date.
Frequently asked questions
How is conception date estimated?
Assuming a standard 28-day cycle, ovulation (and likely conception) occurs around day 14 after the start of the last menstrual period.
Can this tell me the exact day I conceived?
No — it's an estimate based on average cycle timing. Actual ovulation can shift earlier or later depending on your individual cycle length — the Ovulation Calculator lets you enter your own cycle length for a more personalized estimate.
How does this relate to my due date?
Your due date (Naegele's rule) is set at 280 days from your last period, which works out to about 266 days after this estimated conception date.
Related calculators
Related articles
Sources
- Methods for Estimating the Due Date — American College of Obstetricians and Gynecologists (ACOG). Effective 01-05-2017, checked 13-09-2026.
This calculator provides a general estimate only and does not constitute personalized medical advice.
Report a calculation issue