There are two nifty gadgets that are commonly used to give equally sized slices from each pizza, every time. This has gone from just important to critical for some stores as they are providing sliced pizza to local schools where each slice MUST be the same as the others. The first thing is called "The Equalizer" from Lloyd Pans. This is something like a large round rocker knife that is pushed down into the pizza to cut it into equally sized portions. The other one is a composite board with different size circles on it and lines that intersect in the middle of the board. You place the pizza in the correct size circle and just cut with your pizza wheel using the correct intersecting lines as a guide to get the number of slices needed from the pizza. I've used both and they work as advertised.
Tom Lehmann/The Dough Doctor