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

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)

Pregnancy

Gestational Age Calculator

Converts the number of days since your last menstrual period into gestational age expressed as weeks and days. Use it at any point in pregnancy to know your exact stage for prenatal care, screenings, and milestone tracking.

Days since Last Menstrual Period (days)

Key differences

	Due Date Calculator (Naegele's Rule)	Gestational Age Calculator
Category	Pregnancy	Pregnancy
Inputs required	3	1
Result	Days until estimated due date (days)	Gestational age (weeks)
What it does	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.	Converts the number of days since your last menstrual period into gestational age expressed as weeks and days. Use it at any point in pregnancy to know your exact stage for prenatal care, screenings, and milestone tracking.