Pregnancy Conception Calculator
Estimate your conception date and likely conception window from your due date or last period.
Sperm can survive 3–5 days and the egg about 24 hours, so the likely window spans several days around the estimated conception date.
Worth Knowing
Working backward from a due date or last period, this estimates when conception likely occurred — useful for narrowing down a window rather than pinpointing a day. The estimate assumes ovulation around day 14 of a regular cycle, so it drifts for longer, shorter, or irregular cycles. Because sperm can survive several days before fertilization, the actual conception could fall a few days either side of the estimate, which is why medical dating relies on ultrasound rather than a back-calculation.
How to Use
- Enter I know my... into the first field of the Pregnancy Conception Calculator.
- Fill in the rest: Date.
- Your result appears instantly as you type — there's no submit button or page reload.
- Sperm can survive 3–5 days and the egg about 24 hours, so the likely window spans several days around the estimated conception date.