Pregnancy calculator

Use the drop-down menu to calculate your due date or current weeks of pregnancy. This includes by dates, ultrasound dates, conception date or gestation.

This calculator allows you to calculate the following:

Last Menstrual Period (LMP): The LMP calculation uses the standard method of the first day of your last menstrual period plus 280 days to calculate the due date.

Ultrasound Due Date: If a due date has been calculated from an ultrasound in the first trimester, the reverse calculation method is preferred. This calculates the current gestational age and gives an estimated date of LMP.

Conception Date: If conception is known (e.g. date of insemination, ovulation or egg retrieval), then the due date can be calculated by adding 266 days.

Gestation at future or past date: Use to calculate gestation in the future or past. First, calculate current gestation using one of the other methods, then go to this section and choose past or future date.

Date at future or past gestation: Use to calculate the date at a specific gestation (enter in weeks). First, calculate current gestation using one of the other methods, then go to this section and choose a gestational age.

Credits: Dr Jeremy Steinberg, GP & Programmer, Auckland, NZ.