Do the calculator, then add 4 feet. You can make it shorter, you can't make it longer. 3/16 beverage tubing, not vinyl hose from the hardware store.
And, you need to understand what you're doing.
The beer is under pressure. As it flows down the tubing it encounters friction along the side walls and the pressure drops. If the lines were long enough the beer would stop flowing entirely. You want to *balance* the pressure of the keg with the losses due to serving height, and friction along the lines, so that the beer is neat atmospheric pressure as it exits the tap. Too much line loss and the beer pours too slowly. Not enough loss and the beer turns to foam when it exits the tap and experiences a sudden pressure drop to atmosphere. ( kinda like shaking up a can of beer (increase pressure by forcing co2 out of solution) and suddenly open the top. The calculator is based on beverage tubing, which has a known coefficient of friction. Vinyl tubing has a slicker inside and as a result much less friction, therefore requiring much more length to make up the same friction losses. We as home brewers have these issues because we have no real need for extended serving lines. Commercial dispensing systems ( like in a bar) may have the kegs remotely located from the tap. Some bars even have their kegs located in a cooler near the loading dock.
Oh, and get yourself flow control taps next time you're shopping. It allows you to tweak the pressure at the tap discharge *somewhat*. Not a solution for lines too short, but will help you accommodate a wider variety of carb levels and resultant pressure out of the keg.
