I think we all know what you're referring to (steam-engine, coiltoy, etc), but trust someone who says "don't just follow a calculator".
I started rebuilding EVOD BCC heads for my ego batteries. Shooting for 1.8 ohms, didn't have anything to check resistance, it turned out to be 2.2: 20% more than I wanted.
Got myself my first rebuildable atomizer the other day, and a VTR for use/checking resistance. I wanted a 1.3 ohm coil, ended up with a 0.9 ohm coil: almost 45% less resistance than I wanted. In the dangerous direction. Suffice to say, tossed that one and built another.
I wanted a 10/9 wrap, who knows what it ended up being. It's very, very hard to count how many wraps make up the microcoil you've just built.
I used coil calculators each time, but sometimes these things just happen. It is absolutely necessary if using a mech mod, or building even moderately low resistance coils, for me.
ETA: especially with the paps, a (beautiful) mech mod and your first time rebuilding, I would expect a short at some point. They is not good when your PV isn't regulated, and I'm sure you know that.