Conception Calculator
When you most likely conceived
Conception
16 July 2026Thursday
11 July 2026
Fertile window began
17 July 2026
Fertile window ended
8 April 2027
Due date
Sex most likely to have led to pregnancy
Saturday, 11 July 2026 to Friday, 17 July 2026
- 1Pick your known dateDue date or last period
- 2Enter itPlus cycle length if known
- 3See the windowLikely conception dates
How is conception dated?
Conception usually happens around ovulation, about 2 weeks after the first day of a 28-day cycle, or 266 days before the due date.
Conception ≈ due date − 266 days
Likely window = 5 days before to 1 day after
Why it's a window, not a day
Sperm can survive up to about 5 days, and the egg about a day. So sex on any of the 5 days before ovulation, or the day after, can lead to pregnancy.
Related calculators
Frequently asked questions
Can I find the exact day I conceived?
Not from dates alone. Cycles vary, so this gives the most likely date and a window of about a week around it.
How many weeks after conception is my due date?
About 38 weeks (266 days).
Does an IVF transfer date give an exact conception date?
Much closer, yes. Use the Pregnancy Calculator's IVF options for IVF due dates.
Sources
- ACOG Committee Opinion 700: Methods for estimating the due date, 2017
- Wilcox AJ et al. The timing of the fertile window in the menstrual cycle. BMJ, 2000
Last reviewed: October 2026