I used the sizing calculator at competitive cyclist and came up with 83.5cm inseam, trunk 58.7cm, forearm 32cm, arm 64.5cm, thigh 58.7cm, lower leg 53cm, sternal notch 141cm, total body height 174cm.

Anyway, depending on "competitive fit", "Eddy fit" and "French fit", it appears I need a top tube of either 51.8 to 53.4cm.

So, what in the world does this mean? I know a Trek shop measure my inseam and told me I could take either a 51cm or 54cm in a 520 but what does this 51.8 to 53.4cm translate to?

You're touching on what's more important, standover or effective top tube length.

For me, it's tt length. This determines where my sit bones will land on the saddle and how stretched out I'll be. The tt length needs to be as close to perfect as possible so as to minimize the need for mods and keep the over all geometry within reasonable bounds. Helps if your body geometry is close to industry standards for stock frame construction.

You can measure 'til the cows come home, but the only way to find out if a bike is for you is to ride it. A lot.

Sounds like you need to look at the Trek website, find the model you're interested in, then look at their "Fit & Sizing" chart. It will show you the effective top tube length for each of the different sizes. You can compare the numbers from the sizing chart to your 51.8-53.4cm goal.

A word of warning: while I found the numbers for the Competitive Fit and the Eddy Fit to be reasonable, the French Fit put me on a frame that was enormous! There was less drop between the saddle and bars, but the lengthy top tube and resulting reach had me so stretched out I felt like I was ready to ride a Time Trial rather than a touring bike! I ended up using the Eddy fit for my road and touring bikes...

Better still walk into the shop and talk to people..
my fit system is based on 40 years.
of trying stuff..

what riding posture did you seek race aero tuck or sit up and look around,
or somewhere in-between?

Go with Top tube measurement. My road bike is 59cm. My old Trek 5900 was a 62cm and my Cannondale Synapse is a 60cm frame size. Both have 59cm top tubes. My Surly is a 60cm frame with a 59 top tube but with a shorter stem for more upright position. Best to find a shop that does fitting if your not sure. Our shop does them and people are happy with their bike after.

Those are fit calculators for road bikes.

That's not exactly the same as fit for a touring bike, although can be close. I'm assuming you're interested in a touring bike fit since you posted in Touring forum.

Touring bikes are typically fitted with shorter reach/TT, higher handlebar position, and perhaps a lower BB. There is an emphasis on comfort for longer rides, and ease/safety of operation. Road bikes are obviously more about performance.

If you're looking at setting up a dedicated Tourer with a flat bar (like a hybrid), then that's a whole other thing again.

Fit calculator results are a good starting point, but sometimes you end up a long ways away from what the 'puter says.

As others have stated, reach/effective TT length is where you focus for fit. Everything else is secondary consideration.

You should go try on some bikes at the LBS.

second or third or fourth the tt measurement being so important--and take into account both stem length AND drop bar "depth" for want of a better word, some drop bars vary in the distance from topbar area to where teh brake hoods are (and consequently could put you out further than another set of bars, same stem and same tt)

also, dont forget how people are proportioned differently. Im 5'10.5 and fit a 54-55 tt very well, on paper at my height and inseam, a longer tt is often recommended.

Would larger tires like 700x42 make any difference in fit? I mean larger tires would raise the bike.

No. What matters in fit is the distance between your contact points - seat, hands, feet. Those things don't change no matter how high the bike is off the ground, which is why a penny-farthing can fit you.

The only possible difference tyres can make is to the stand over height, and if that is so tight as to be affected by the tyres you choose, the bike is more than likely too big for you anyway.

Have a read of Peter White's fit guide, it is more suitable for tourists than most.