I know D'Addario has a PDF that breaks a bunch of things down but I'm mostly looking to compare a few different gauges to different scale lengths. Is there some sort of calculator online that does the formula for you?

For example, .009 E string on a 27" scale length guitar compared to a .010 E string on a 25.5" scale length guitar.
not that i know of but a difference in scale length is a couple of pounds at most

27" is baritone so if you were considering tuning to E standard on one then I'd get really light strings, .010's or less
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Try this link:

It will let you enter every parameter- it is just not that obvious.
The "top window" lets you select a couple of typical string set gauges, as well as scale length.
But below that you can enter each string guage individually, as well as what it is tuned to.
Much appreciated.

To further the discussion, is there any reason NOT to try to get the string gauges to create roughly the same tension? From what I see there is a difference between wound and plain strings (would be great if someone could explain this).

I typically play on Dunlop .010's but the different gauges just don't feel right. My low E and G strings aren't tense enough and my high E is a bit too much. I'm hoping I can calculate what string gauges would give a similar "feel" as far as tension goes. I'm also looking at some slightly longer scale lengths (between 25.7" to 27").