Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Conception Date Estimate Calculator

Estimate how many days ago conception likely occurred from your last menstrual period, corrected for your cycle length and luteal phase rather than assuming day-14 ovulation.

Days since first day of last period (LMP) (days)

Average menstrual cycle length (days)

Luteal phase length (days)

Pregnancy

Due Date Calculator (Naegele's Rule)

Estimate your due date from your last menstrual period using Naegele's rule, adjusted for your actual cycle length and luteal phase so a non-28-day cycle isn't misdated.

Days since first day of last period (LMP) (days)

Average menstrual cycle length (days)

Luteal phase length (days)

Key differences

	Conception Date Estimate Calculator	Due Date Calculator (Naegele's Rule)
Category	Pregnancy	Pregnancy
Inputs required	3	3
Result	Days since estimated conception (days)	Days until estimated due date (days)
What it does	Estimate how many days ago conception likely occurred from your last menstrual period, corrected for your cycle length and luteal phase rather than assuming day-14 ovulation.	Estimate your due date from your last menstrual period using Naegele's rule, adjusted for your actual cycle length and luteal phase so a non-28-day cycle isn't misdated.