This free app allows users of propositional logic to perform operations with the same ease as that offered by a mathematical calculator. It facilitates learners of logic by providing considerable feedback. To be precise, using this app, one can determine whether: (1) input is well-formed and, if not, why not, (2) sentences are tautologies, contradictions or contingent, (3) sets of sentences are consistent or inconsistent and (4) arguments are valid or invalid. It also produces truth tables which can be copied into other applications. As of this version, the calculator is restricted to semantic operations.