Conception Date Calculator

Work backwards (or forwards) to estimate conception, ovulation, due date and current pregnancy week — from whatever date you already know.

First day of last menstrual period

Day 1 of your most recent period.

Average cycle length

How it works
Naegele’s rule: due date = LMP + 280 days. Conception typically happens around day 14 of a 28-day cycle (ovulation + ~24 h).

Only ~4% of babies arrive exactly on their due date — most come in the two weeks around it. Ultrasound dating is the most accurate.

📅 Three starting points

LMP, due date or conception date.

🥈 Ovulation window

See the 5-day fertile window.

🧪 Week counter

Current week and days pregnant.

📖 Naegele's rule

The classic 280-day estimate.

Conception Date Calculator

📅 Three starting points

🥈 Ovulation window

🧪 Week counter

📖 Naegele's rule

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