2015 MLB Relative Power Index (RPI),as of the games of July 21,2015 from ESPN.GO.COM

MLB RPI Rankings
RK	TEAM	RPI	W	L	PCT	SOS	PWR	RS	RA	EXPW-L	EXPWP
1	St. Louis Cardinals	.541	59	34	.634	.510	1	379	276	61-32	.653
2	Kansas City Royals	.536	56	36	.609	.511	3	405	339	54-38	.588
3	Chicago Cubs	.522	50	42	.543	.515	10	354	333	49-43	.531
4	Pittsburgh Pirates	.518	54	39	.581	.498	2	374	320	54-39	.577
5	Los Angeles Angels	.516	53	40	.570	.498	6	397	339	54-39	.578
6	New York Yankees	.515	51	41	.554	.501	7	421	393	49-43	.534
7	Minnesota Twins	.515	50	43	.538	.507	8	391	384	47-46	.509
8	Detroit Tigers	.512	46	47	.495	.517	16	422	443	44-49	.476
9	Houston Astros	.510	52	43	.547	.498	9	422	357	55-40	.583
10	Los Angeles Dodgers	.507	53	42	.558	.490	4	396	332	56-39	.587
11	Toronto Blue Jays	.501	48	47	.505	.499	15	505	410	57-38	.603
12	Cleveland Indians	.501	44	48	.478	.508	17	363	387	43-49	.468
13	Washington Nationals	.500	50	42	.543	.486	5	388	357	50-42	.542
14	Tampa Bay Rays	.500	48	48	.500	.500	14	341	358	46-50	.476
15	New York Mets	.500	49	45	.521	.493	12	326	337	45-49	.483
16	Chicago White Sox	.500	42	49	.462	.512	21	308	388	35-56	.387
17	Baltimore Orioles	.497	46	46	.500	.497	13	404	361	51-41	.556
18	San Diego Padres	.497	44	50	.468	.507	25	368	417	41-53	.438
19	Milwaukee Brewers	.496	42	52	.447	.512	28	386	417	43-51	.461
20	Seattle Mariners	.496	43	51	.457	.509	23	335	383	41-53	.433
21	San Francisco Giants	.495	50	44	.532	.482	11	404	368	51-43	.547
22	Oakland Athletics	.494	43	52	.453	.507	24	408	361	53-42	.561
23	Texas Rangers	.493	44	49	.473	.500	22	395	422	43-50	.467
24	Arizona Diamondbacks	.489	43	49	.467	.496	18	405	412	45-47	.491
25	Cincinnati Reds	.487	41	50	.451	.499	26	353	403	40-51	.434
26	Boston Red Sox	.485	42	52	.447	.498	19	383	449	40-54	.421
27	Atlanta Braves	.482	45	49	.479	.483	20	363	403	42-52	.448
28	Colorado Rockies	.473	40	52	.435	.486	27	403	468	39-53	.426
29	Miami Marlins	.471	39	55	.415	.490	29	345	374	43-51	.460
30	Philadelphia Phillies	.456	33	63	.344	.493	30	330	483	31-65	.318

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.