From the Pokemon Showdown repo

Hackmons Cup Level Calculator.js

mbstmin = 1307;

// Type the base stats of the Pokemon in manually here:
hp = 79;
atk = 105;
def = 70;
spa = 145;
spd = 80;
spe = 101;

// This code works out the level (I think!)
mbst = (hp * 2 + 31 + 21 + 100) + 10;
mbst += (atk * 2 + 31 + 21 + 100) + 5;
mbst += (def * 2 + 31 + 21 + 100) + 5;
mbst += (spa * 2 + 31 + 21 + 100) + 5;
mbst += (spd * 2 + 31 + 21 + 100) + 5;
mbst += (spe * 2 + 31 + 21 + 100) + 5;
level = Math.floor(100 * mbstmin / mbst);
while (level < 100) {
		mbst = Math.floor((hp * 2 + 31 + 21 + 100) * level / 100 + 10);
		mbst += Math.floor(((atk * 2 + 31 + 21 + 100) * level / 100 + 5) * level / 100);
		mbst += Math.floor((def * 2 + 31 + 21 + 100) * level / 100 + 5);
		mbst += Math.floor(((spa * 2 + 31 + 21 + 100) * level / 100 + 5) * level / 100);
		mbst += Math.floor((spd * 2 + 31 + 21 + 100) * level / 100 + 5);
		mbst += Math.floor((spe * 2 + 31 + 21 + 100) * level / 100 + 5);
		if (mbst >= mbstmin) break;
		level++;
}

window.alert(level);