This is an online calculator for logic formulas. It can evaluate predicates and formulas given in the B notation. Under the hood, we use the ProB animator and model checker. The above calculator has a time-out of 2.5 seconds, and MAXINT is set to 127 and MININT to -128. You can also download ProB for execution on your computer, along with support for B, Event-B, CSP-M, TLA+, and Z.