Reverse Due Date Calculator
Health & FitnessWork backward from your due date to estimate when conception and intercourse most likely occurred.
Estimated Conception (days ago)
How many days ago conception most likely occurred, based on a standard 280-day pregnancy.
Estimated Earliest Intercourse (days ago)
87
The earliest likely day intercourse leading to conception could have occurred, since sperm can survive several days before ovulation.
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Odeh Ahwal0people find this calculator helpful
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Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
Health & Fitness calculators
Frequently Asked Questions
How does this calculator work backward from a due date?
It assumes a standard 280-day (40-week) pregnancy. Subtracting the number of days remaining until your due date from 280 gives an estimate of how many days ago conception occurred.
Why is the intercourse estimate different from the conception estimate?
Conception itself may not happen the same day as intercourse, since sperm can survive in the reproductive tract for several days before ovulation and fertilization occur.
How accurate is this backward estimate?
Since ovulation and conception timing vary month to month, treat these as estimated ranges rather than exact days.
Can I use a birth date instead of a due date?
Yes, if your baby was born close to their due date, you can use the actual birth date the same way. If the birth was significantly early or late, the estimate will be less accurate.
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