Chess engines strenght is measured by an ELO ranking determined by means of computer tournements with multiple games on standard hardware platforms, so that processor differences are factored out.
Some organizations test computer chess software by playing thousands of games among chess engines and producing a ratings table, published on Internet.
Among these organizations the most famous are CEGT (Chess Engines Grand Tournament) and CCRL (Computer Chess Rating Lists).
Below you can consult their ranking lists with the best 20 engines in different time control situations.
5 minutes + 3 seconds each move
120 minutes for 40 moves + 40 minutes for the following 20 moves + 20 minutes to terminarte the game with further 10 seconds for each extra move played
40 minutes for 40 moves
