Computer Elo
Chess.com computer elo levels are designed to allow humans to be able to beat it, even at the highest level. Granted you need to be a grandmaster to win many games at level 10.
Chess.com owns a chess engine. I think it's komodo.
But in any event, Stockfish is freeware and is about as strong as Komodo.
Komodo, Stockfish, and Houdini are the perpetual top contenders on the chess engine rating sites.
I think the "Top Chess Engine Tournament" is a better indicator of engine strength.
The main chess engine rating site only plays 3 minute games. Supposedly, they are trying to simulate some arbitrary hardware configuration from the Jurassic age of computers. Roughly the year 2005 in human terms, also known as the year of the rooster.