Most TIG welder settings charts or calculators use a formula based on one amp per one thousandths of thickness.
The problem is this formula only holds true up to around .125" 125 thousandths on carbon steel for a 2f fillet weld.
Anything thicker than 125 thousandths, the formula starts being useless.
A good example of this is TIG welding one inch thick aluminum which according to the one amp per one thou rule of thumb would require 1,000 amps.
So TIG welder charts and calculators are not really that helpful.
But what I think is helpful is short videos showing different types of joints and thicknesses with details and settings listed along with clear arc shots.
The links above will take you to quick settings pages with very short concise videos with TIG welder settings for aluminum listed and shown in detail.
How can you beat that?