No calculator per say but a couple of things to consider.
1. a dull router bit will get hot. As will a bit with any resin build up on it.
2. I'm having trouble following this: "Last night I cut a pocket 1/4" square with those settings and the bit was real hot, and discolored at the end. I had the stepover set at .24". The finish was good but the bit is basically ruined." To cut a 1/4" square pocket you would need a real small router bit that can't do a 0.24" step over. Are you cutting a much larger pocket with a 1/4" cutter?
3. While an ideal number will vary with the wood in question, make sure you know what your feed per tooth is for the material you are running. Looks like you are running 0.0048 per tooth, calculator here: Milling Formula Calculator. If this is MDF I might try doubling that feed rate and use a step over that is no more than half the cutters diameter.
4. As for the cutter is it high speed steel or carbide? Generally both can be resharpened. In any event don't throw out old worn or broken, carbide or HSS! Even if they are beyond sharpening for their intended use they have many applications in a machine shop.
5. Finally this pocket, how tight was it. Down cut bits can have issues in pockets in that swarf can become packed in the pocket and cutter. This leads to heating. Actually you can break a bit this way. Depending upon what you are doing with these pockets you might want to try an up cut bit.