Compare calculators

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

Conception Date Calculator

Works backward from how many days remain until a known due date to estimate when conception occurred (and how far along you are). Switch the basis to LMP to account for your cycle length and luteal phase.

Days Until Due Date (days)

Average Cycle Length (days)

Luteal Phase Length (days)

Calculate From

Fill in the required fields to see your result.

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)

Fill in the required fields to see your result.

Key differences

	Conception Date Calculator	Gestational Age Calculator
Category	Pregnancy	Pregnancy
Inputs required	4	1
Result	Estimated Conception	Gestational age (weeks)
What it does	Works backward from how many days remain until a known due date to estimate when conception occurred (and how far along you are). Switch the basis to LMP to account for your cycle length and luteal phase.	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.