Reverse Due Date Calculator
Reverse Due Date
Calculate the estimated conception date and fertile window from a given due date or birth date
weeks
days
Formula
Conception Date = Due Date - (Gestation Weeks x 7) + (Cycle Length - 14)
Frequently Asked Questions
How accurate is a reverse due date calculation?
Reverse due date calculations provide an estimate within a range of about 5 days. Actual conception depends on individual ovulation timing and cycle regularity.
Does cycle length affect the estimated conception date?
Yes. Longer cycles mean later ovulation, so the estimated conception date shifts accordingly. The standard 28-day cycle assumes ovulation on day 14.
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