2015 MLB Relative Power Index (RPI),as of the games of August 4,2015 from ESPN.GO.COM

MLB RPI Rankings
RK	TEAM	RPI	W	L	PCT	SOS	PWR	RS	RA	EXPW-L	EXPWP
1	St. Louis Cardinals	.537	67	39	.632	.505	1	420	311	68-38	.646
2	Kansas City Royals	.531	63	42	.600	.508	2	454	391	60-45	.574
3	New York Yankees	.518	60	45	.571	.500	7	525	455	60-45	.571
4	Chicago Cubs	.518	58	47	.552	.506	10	405	393	54-51	.515
5	Pittsburgh Pirates	.518	61	44	.581	.496	3	429	382	59-46	.558
6	Houston Astros	.514	60	48	.556	.500	5	485	403	64-44	.592
7	Los Angeles Dodgers	.511	60	46	.566	.493	4	438	375	61-45	.577
8	Los Angeles Angels	.508	56	50	.528	.501	8	443	400	58-48	.551
9	Minnesota Twins	.506	54	52	.509	.504	14	440	448	52-54	.491
10	New York Mets	.505	57	50	.533	.496	12	390	377	55-52	.517
11	Toronto Blue Jays	.504	56	52	.519	.499	11	569	457	66-42	.608
12	Detroit Tigers	.502	51	55	.481	.510	17	471	508	49-57	.462
13	Texas Rangers	.502	53	53	.500	.503	15	473	511	49-57	.461
14	San Francisco Giants	.501	58	48	.547	.485	6	466	410	60-46	.564
15	Baltimore Orioles	.501	54	52	.509	.498	13	464	415	59-47	.556
16	Chicago White Sox	.500	50	55	.476	.508	20	390	461	44-61	.417
17	Washington Nationals	.500	55	50	.524	.492	9	433	406	56-49	.532
18	San Diego Padres	.500	52	55	.486	.504	18	422	466	48-59	.451
19	Tampa Bay Rays	.499	54	54	.500	.498	16	399	408	53-55	.489
20	Cleveland Indians	.494	49	57	.462	.505	21	405	444	48-58	.454
21	Arizona Diamondbacks	.494	51	54	.486	.497	19	461	457	53-52	.504
22	Seattle Mariners	.494	50	58	.463	.504	22	403	454	48-60	.441
23	Cincinnati Reds	.492	48	56	.462	.502	24	416	457	47-57	.453
24	Oakland Athletics	.490	48	60	.444	.505	26	446	410	59-49	.542
25	Milwaukee Brewers	.487	45	63	.417	.510	28	420	480	47-61	.434
26	Boston Red Sox	.485	47	60	.439	.500	25	449	524	45-62	.423
27	Atlanta Braves	.478	48	59	.449	.487	23	397	467	45-62	.420
28	Colorado Rockies	.476	44	61	.419	.496	27	480	548	46-59	.434
29	Miami Marlins	.471	43	64	.402	.495	29	377	427	47-60	.438
30	Philadelphia Phillies	.468	42	65	.393	.494	30	394	519	39-68	.366

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.