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creepage to earth is usually from the tab to the nearest earthed metal, input to output is as it says, creepage can be from the pins ( any pin ) to earth or output as is the case required ...
working creepage is for the normal max internal ckt, safety creepage is different, usually at least 5mm in to out ( 230Vac ) and 3.2mm to earth
Software can only give you clearance distance (smallest separation between two copper objects). As creepage is the distance over surfaces, it is not always as easy to calculate, so no easy way to measure it... I tend to draw a polyline and use the length of that if the surface is flat, this suffices for most PCB's.
Creepage is always greater than clearance so either leave enough gap to satisfy the creepage requirements, where this is not possible (between connector pins) you can add a slot 1mm or wider to increase the creepage distance.
creepage to earth is usually from the tab to the nearest earthed metal, input to output is as it says, creepage can be from the pins ( any pin ) to earth or output as is the case required ...
working creepage is for the normal max internal ckt, safety creepage is different, usually at least 5mm in to out ( 230Vac ) and 3.2mm to earth
Creepage is creepage and is dependant on the specification you are working to, there is no working creepage... and don't quote figures, again creepage depends on the envoironment the PCB is going to be subjected to, as creepage is a tracking voltage, surface pollutants come into play, you are quoting clearance distances.
The minimum required creepage distance over an insulating material between electrically conducting parts in apparatus, especially between parts with a high voltage and parts that can be touched by human users, is dependent on the insulator's CTI value. Creepage distance requirement depends on the CTI. A higher CTI value means a lower minimum creepage distance required, and the closer two conductive parts can be. CTI value is determined in IPC rulebook.
Note that it's unlikely the pins of your TO-220 are across a safety isolation barrier. Primary-to-primary or secondary-to-secondary spacing are more of a problem for you and product reliability than the safety standards.
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