Compare calculators

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

Conception Date Calculator

Estimates how many days ago conception occurred from a reference point — your due date, last menstrual period, or an ultrasound dating scan — entered as days since that reference (negative if it is a future due date).

Calculate From

Days Since Reference Date (use a negative number for a future due date) (days)

Cycle Length (days)

Ultrasound Gestational Age (weeks)

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	Estimates how many days ago conception occurred from a reference point — your due date, last menstrual period, or an ultrasound dating scan — entered as days since that reference (negative if it is a future due date).	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.