Calibration Cube 40x40x40

I'm very new to this. I'm sure to some veteran 3D makers this elementary. For a beginner, trying to make my first machine do what it's supposed to (or what I want it to anyway) this calibration tool has changed everything. Nothing was quite fitting until now. Everything I print fits exactly how it's supposed to now.

Made a new one that's a faster print and very little filament waste. The x&z arc should come out a smooth 40mm from corner to edge as you pass your calipers over the crescent with the opposite corner as a pivot. Additionally you have all 3 axis measurable separately. The inside of the bottom square should be 36mm X and Y if your settings are ideal.
It only akes 6 grams of PLA to check your settings.

Handy way to check and see if your steps per mm are calibrated correctly. Then apply a basic balanced fraction equation to change the steps per mm on your system if your cube doesn't come out 40x40x40 as intended.

(X Steps Per mm of Print * 40)/(Printed X