Pregnancy progress
Trimester bands with a pointer at your current gestational week.
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Pregnancy Conception Calculator
Work backward from your due date or last period to estimate when you likely conceived, plus the surrounding conception window.
Estimated conception date
—
Conception window—
Last menstrual period—
Due date—
How it works
Conception usually happens about 14 days after the start of the last period and roughly 266 days before the due date. Because sperm can survive several days, the exact day is uncertain, so the calculator also shows a short conception window around the most likely date.
Conception ≈ due date − 266 days
Conception ≈ LMP + 14 days
Window ≈ conception − 3 to + 2 days
Conception ≈ LMP + 14 days
Window ≈ conception − 3 to + 2 days
Frequently asked questions
Can this tell me exactly when I conceived?
No. It gives the most probable date and a short window. Ovulation timing and sperm survival mean the true date can be a few days either side.
Which input is most reliable?
An ultrasound-based gestational age is usually the most accurate, followed by a known due date, then the last period.