About

This calculator bridges the gap between trying to conceive and pregnancy planning. It answers the question: "If I get pregnant this cycle, when will the baby arrive?" It is particularly useful for parents attempting to time a birth for a specific season or academic year. The calculation uses Naegele's Rule adjusted for cycle length, providing a complete timeline from the Last Menstrual Period (LMP) to the projected delivery date.

Formulas

The core projection relies on aligning the biological due date with the ovulation date rather than just the LMP.

EDD = LMP + 1 year − 3 months + 7 days + Adjustment

Where Adjustment = Cycle Length − 28.

Reference Data

Event	Formula / Logic	Notes
Fertile Window	LMP + (Cycle − 19) to (Cycle − 13)	Best time for intercourse.
Implantation	Ovulation + 6 - 10 days	Earliest time for a positive test.
Due Date (Standard)	LMP + 280 days	Assumes 28-day cycle.
Adjusted EDD	LMP + 280 + (Cycle − 28)	Corrects for long/short cycles.

Frequently Asked Questions

It is a statistical estimation. Only about 4% of babies are born on their exact due date. However, this calculation gives you the most medically accurate "target week" based on your current cycle.

Pregnancy duration is calculated as 266 days from conception. Since ovulation (conception) happens later in a longer cycle, the due date must be pushed back by the same number of days.

You should wait until at least 12-14 days after the calculated ovulation date (the 'Two Week Wait') to avoid false negatives.