int v = 30000; // 32-bit word to find the log base 2 of
int r = 0; // r will be lg(v)

while ( (v >>= 1) != 0) // unroll for more speed...
{
  r++;
}

Math.Floor(Math.Log(30000, 2)) + 1

(int) Math.Log(30000, 2) + 1