2015 MLB Relative Power Index (RPI),as of the games of August 9,2015 from ESPN.GO.COM

MLB RPI Rankings
RK	TEAM	RPI	W	L	PCT	SOS	PWR	RS	RA	EXPW-L	EXPWP
1	St. Louis Cardinals	.539	71	40	.640	.505	1	440	319	73-38	.655
2	Kansas City Royals	.531	66	44	.600	.508	2	476	413	63-47	.571
3	Pittsburgh Pirates	.523	65	44	.596	.498	3	460	402	62-47	.567
4	Chicago Cubs	.522	62	48	.564	.508	10	432	413	57-53	.522
5	New York Yankees	.514	61	49	.555	.501	7	529	468	62-48	.561
6	Toronto Blue Jays	.510	61	52	.540	.500	11	597	468	70-43	.619
7	Los Angeles Dodgers	.509	62	49	.559	.493	4	467	410	63-48	.565
8	Houston Astros	.509	61	52	.540	.499	5	499	421	66-47	.584
9	Los Angeles Angels	.509	59	51	.536	.500	8	460	416	61-49	.550
10	New York Mets	.505	59	52	.532	.496	12	409	395	57-54	.517
11	Detroit Tigers	.503	54	57	.486	.509	17	492	535	51-60	.458
12	Minnesota Twins	.503	55	56	.495	.505	14	465	500	51-60	.464
13	Baltimore Orioles	.501	56	54	.509	.498	13	484	431	61-49	.558
14	Texas Rangers	.501	55	55	.500	.501	15	493	525	52-58	.469
15	Tampa Bay Rays	.500	56	56	.500	.500	16	416	425	55-57	.489
16	Chicago White Sox	.499	51	58	.468	.509	20	408	481	46-63	.418
17	Washington Nationals	.498	57	53	.518	.492	9	459	432	58-52	.530
18	San Francisco Giants	.497	59	52	.532	.486	6	485	433	62-49	.556
19	Cleveland Indians	.495	51	59	.464	.505	21	442	463	52-58	.477
20	Seattle Mariners	.494	52	60	.464	.503	22	419	477	49-63	.436
21	Arizona Diamondbacks	.493	54	56	.491	.494	19	482	476	56-54	.506
22	San Diego Padres	.492	52	60	.464	.501	18	436	497	49-63	.435
23	Cincinnati Reds	.492	49	60	.450	.506	24	426	471	49-60	.450
24	Oakland Athletics	.492	51	62	.451	.505	26	463	428	61-52	.539
25	Milwaukee Brewers	.491	48	65	.425	.513	28	443	499	50-63	.441
26	Boston Red Sox	.487	50	62	.446	.501	25	472	538	49-63	.435
27	Atlanta Braves	.478	51	61	.455	.486	23	421	490	48-64	.425
28	Colorado Rockies	.478	47	62	.431	.494	27	499	567	48-61	.436
29	Philadelphia Phillies	.471	45	67	.402	.494	30	418	541	42-70	.374
30	Miami Marlins	.467	44	68	.393	.491	29	400	458	48-64	.433

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.