The gestational wheel calculator of the current invention greatly extends the function and usefulness of the basic gestational calculation wheel by providing increased accuracy of gestational dates by using an average cycle length adjuster, provides paternity information using a sperm exposure marker, provides more accurate ultrasound and other test measurements by using scales printed parallel to gestational age, and provide a means of accurately aligning these measurements with the proper calendar or gestational date by including a transparent marker arm. In addition, normal range and error functions are included on the marker arm. A one-fourth year window is used to increase the surface area of information available for viewing charts, tables, and promotions on the underlying base plate. Easier reading of the calculator is provided by special markers for the first day of each calendar month and by providing sub-marks for each day within a gestational week. Scheduling conflicts are improved by providing a weekday scale covering the entire nine month duration of pregnancy. The other side of the gestational wheel can be used to provide additional promotional or informational items including rotating transparent windows to display additional surface area, to provide means of calculating algorithm solutions for body mass index, and display observational data for EFW, delta OD 450, and AFI.