Mobile OB Wheel (also known as pregnancy calculator and obstetrics disc) lets you calculate following dates and values:
- first day of a woman's last menstrual period
- date of conception
- end of 1st trimester
- end of 2nd trimester
- expected date of delivery
- weeks gestational age.

Fill in one of above mentioned values to calculate the rest.
Change of examination date lets you calculate weeks gestational age for picked date.

App works basing of Naegele's rule - expected date of delivery is exactly 280 days after woman's last menstrual period. Little variations are possible.