Abstract: A pocket-sized, electronic gestational calculator includes a housing sized and shaped to fit into a user's pocket, an input device connected to the housing and configured to produce signals in response to actuation of the input device by the user, an electronic processor positioned in the housing and configured to receive the signals from the input device and to process the signals to produce gestational information, and a display connected to the housing and configured to display the gestational information produced by the electronic processor. Gestational information produced and displayed includes the expected due date and the gestational age in weeks, months and trimesters.