I use the basic calculator that came with the phone. I don't know if this is on me, but I often have no way to clear the data in the calculator (using an AC or similar button). Sometimes the AC button shows and things are okay. Sometimes not. There is never a C (clear) button available. Sometimes, pressing the equal (=) button resets everything. But oftentimes, nothing but resetting the phone clears the calculator memory. I'll look around for another calculator, but I thought this was a crazy situation.