Question about powering a nano and a DC motor

Hello! I've been experimenting with powered arduinos an really i know nothing. I have a 130 dc motor from adafruit and a nano clone, powered them with a 12V 23A each, one passed through a voltage regulator which outputs 5v to the arduino.

This battery is choosen by the limitations of the enclosure of which i put this things (I'm making a april fools prank, will share soon :D)

My question is, how can i calculate how much power will the arduino draw from the battery just to stay on, and can i power the two devices with just one battery, whit one output passed through the regulator and the other clean 12v?