for the jumps between gears in PERCENTAGE, use the sheldon brown gear calculator, it shows very clearly the percentage jump between each shift, ie 12%, 9%, 16% whatever.
Is a great way to compare cassettes to get an idea of jumps--but you do have to have some experience with a given cassette and know the jumps to relate the difference, and to know how this will feel riding.
touring or general riding can have slightly large jumps that feel ok using, but being aware of what feels ok for you is whats important, and balancing this against what you need gearing wise for a given weight of the bike and terrain.
again, from a touring perspective, we are more aware of how we need lower gear inch numbers that take priority over a closely spaced cassette, and live with the compromises.