Pregnancy calculation for weeks


I have some problem calculating weeks. So, it would like last menstrual period - today (or specific date) then will get the number of weeks.

as of now, I only found difference-in-months, when I try this as "difference-in-weeks(${pregnant_date},${specific_date}), and I will only get an error from the front-end of the app, “Error loading form. Please try again or check with an administrator.”

Thanks for helping me.

Unfortunately, we do not have a handy function for calculating difference in weeks like difference-in-months. However, I think the default pregnancy form has a good example of doing the exact calculation you are looking for!

The relevant part is as follows (where lmp_date_8601 holds the date value of the recorded last menstrual period):

type name calculation
calculate days_since_lmp floor(decimal-date-time(today())) - decimal-date-time(…/lmp_date_8601)
calculate weeks_since_lmp round(…/days_since_lmp div 7, 2)
calculate weeks_since_lmp_rounded floor(…/days_since_lmp div 7)

Basically, the decimal-date-time function makes it easy to calculate the difference in days between two dates. Then just divide by 7 to get the weeks value.