Android How do you get total memory RAM in the device?

I can get total available memory by:

ActivityManager activityManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();
activityManager.getMemoryInfo(memoryInfo);
memoryInfo.availMem;

However, how do you get Total memory (RAM) of the device?

I did read: How do I discover memory usage of my application in Android?

It doesn't seem like adding pidMemoryInfo.getTotalPss() gives me the total memory either.