2015 MLB Relative Power Index (RPI),as of the games of September 5,2015 from ESPN.GO.COM

MLB RPI Rankings
RK	TEAM	RPI	W	L	PCT	SOS	PWR	RS	RA	EXPW-L	EXPWP
1	St. Louis Cardinals	.540	87	48	.644	.505	1	550	411	87-48	.642
2	Kansas City Royals	.534	82	53	.607	.509	2	603	516	78-57	.577
3	Pittsburgh Pirates	.523	80	54	.597	.498	3	567	493	76-58	.569
4	Chicago Cubs	.520	77	57	.575	.502	5	558	527	71-63	.529
5	Toronto Blue Jays	.519	77	58	.570	.501	4	737	544	87-48	.647
6	New York Yankees	.516	75	59	.560	.501	9	653	568	76-58	.569
7	Minnesota Twins	.512	70	65	.519	.510	14	582	593	66-69	.491
8	Houston Astros	.512	74	62	.544	.501	7	588	487	81-55	.593
9	Los Angeles Dodgers	.511	77	58	.570	.491	8	553	484	76-59	.566
10	Texas Rangers	.508	71	63	.530	.501	11	591	616	64-70	.479
11	New York Mets	.505	75	60	.556	.488	6	562	502	75-60	.556
12	Chicago White Sox	.505	64	70	.478	.514	20	523	568	61-73	.459
13	Los Angeles Angels	.503	68	67	.504	.503	12	541	554	66-69	.488
14	Cleveland Indians	.502	65	69	.485	.508	18	546	551	66-68	.495
15	Tampa Bay Rays	.502	67	68	.496	.504	17	511	524	66-69	.487
16	Detroit Tigers	.502	62	73	.459	.516	22	588	680	58-77	.428
17	San Francisco Giants	.498	70	66	.515	.493	10	577	523	75-61	.549
18	Baltimore Orioles	.498	65	70	.481	.503	15	587	555	71-64	.528
19	Washington Nationals	.496	70	65	.519	.489	13	592	541	74-61	.545
20	Seattle Mariners	.496	65	71	.478	.502	23	546	627	59-77	.431
21	Boston Red Sox	.493	63	72	.467	.502	21	618	653	64-71	.472
22	San Diego Padres	.492	65	71	.478	.496	19	559	605	63-73	.461
23	Milwaukee Brewers	.491	60	75	.444	.507	26	557	611	61-74	.454
24	Arizona Diamondbacks	.488	65	71	.478	.492	16	608	597	69-67	.509
25	Oakland Athletics	.485	58	78	.426	.505	24	566	565	68-68	.501
26	Cincinnati Reds	.481	55	79	.410	.505	27	538	604	59-75	.442
27	Colorado Rockies	.474	56	79	.415	.493	28	610	708	58-77	.426
28	Miami Marlins	.468	56	80	.412	.487	30	505	564	61-75	.445
29	Philadelphia Phillies	.464	53	83	.390	.489	29	527	699	49-87	.362
30	Atlanta Braves	.463	54	82	.397	.485	25	484	657	48-88	.352

Glossary

• W: Wins
• L: Losses
• PCT: Winning percentage
• RPI: Relative Power Index+
• SOS: Strength of schedule

• PWR: ESPN Power Ranking
• RS: Runs scored
• RA: Runs allowed
• EXW-L: Expected W-L*
• EXWP: Expected winning percentage*

+The basic formula is 25% team winning percentage, 50% opponents' average winning percentage, and 25% opponents' opponents' average winning percentage.
*ExW-L and ExWP are derived from Bill James' Pythagorean theorem of baseball: Runs scored [squared] / (Runs scored [squared] + runs allowed [squared]). This formula was designed to relate a team's runs scored and runs allowed to its won-lost record.