Aroldis Chapman has the best career ERA by an active pitcher, with an ERA of 2.52.

Interpreted as:

best career era with a minimum of 750 IP current players

	NAME	ERA	IP	G	W	L	W%	GS	SO	CG	SHO	SV	H	ER	R	HR	BB	HBP	GF	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	ERA-	FIP	FIP-	H/9	PRAA
1	Aroldis Chapman A. Chapman	2.52	821.1	863	60	47	.561	0	1,331	0	0	367	475	230	255	54	408	33	563	7	3,341	87	14.58	4.47	3.26	0.59	39.8	12.2	1.08	.278	2.79	61	2.36	57	5.20	161.8
2	Clayton Kershaw C. Kershaw	2.54	2850.0	454	222	96	.698	450	3,045	25	15	0	2,189	804	881	235	712	46	1	28	11,258	107	9.62	2.25	4.28	0.74	27.0	6.3	1.02	.271	2.78	65	2.85	70	6.91	373.3
3	Kenley Jansen K. Jansen	2.57	927.1	934	54	40	.574	0	1,278	0	0	475	610	265	284	88	282	32	700	20	3,680	21	12.40	2.74	4.53	0.85	34.7	7.7	0.96	.261	2.76	65	2.62	64	5.92	147.2
4	Jacob deGrom J. deGrom	2.57	1539.2	248	96	65	.596	248	1,851	4	2	0	1,173	440	477	146	345	25	0	13	6,045	30	10.82	2.02	5.37	0.85	30.6	5.7	0.99	.279	2.79	66	2.70	66	6.86	239.5
5	Craig Kimbrel C. Kimbrel	2.59	820.2	850	56	48	.538	0	1,280	0	0	440	492	236	263	75	346	40	655	11	3,303	70	14.04	3.79	3.70	0.82	38.8	10.5	1.02	.267	2.88	63	2.61	64	5.40	131.3
6	David Robertson D. Robertson	2.93	893.1	880	68	46	.596	1	1,175	0	0	179	674	291	315	81	364	25	358	38	3,686	57	11.84	3.67	3.23	0.82	31.9	9.9	1.16	.291	3.17	70	2.97	70	6.79	122.3
7	Chris Sale C. Sale	3.01	2078.1	392	144	88	.621	312	2,570	16	3	12	1,688	696	749	213	485	130	25	15	8,367	48	11.13	2.10	5.30	0.92	30.7	5.8	1.05	.297	3.24	71	2.88	69	7.31	301.4
8	Max Fried M. Fried	3.03	1079.2	200	92	41	.692	183	1,052	6	4	0	947	364	405	90	297	45	10	6	4,415	47	8.77	2.48	3.54	0.75	23.8	6.7	1.15	.292	3.38	71	3.25	78	7.89	112.1
9	Tarik Skubal T. Skubal	3.08	766.2	137	54	37	.593	134	889	1	1	0	614	262	287	90	172	26	1	0	3,056	11	10.44	2.02	5.17	1.06	29.1	5.6	1.03	.279	3.37	75	3.14	76	7.21	84
10	Blake Snell B. Snell	3.15	1158.0	222	81	62	.566	222	1,440	1	1	0	891	405	440	111	521	11	0	6	4,791	86	11.19	4.05	2.76	0.86	30.1	10.9	1.22	.288	3.42	77	3.31	79	6.92	111.8
11	Corbin Burnes C. Burnes	3.15	968.0	210	63	38	.624	149	1,114	0	0	2	756	339	374	104	280	38	16	3	3,914	42	10.36	2.60	3.98	0.97	28.5	7.2	1.07	.274	3.48	75	3.25	78	7.03	100.7
12	Gerrit Cole G. Cole	3.18	1954.0	317	153	80	.657	317	2,251	8	5	0	1,627	690	740	217	500	61	0	8	7,861	58	10.37	2.30	4.50	1.00	28.6	6.4	1.09	.292	3.41	79	3.16	77	7.49	213.5
13	Max Scherzer M. Scherzer	3.22	2963.0	483	220	117	.653	474	3,489	12	5	0	2,433	1,059	1,132	354	779	114	2	20	11,987	80	10.60	2.37	4.48	1.08	29.1	6.5	1.08	.287	3.44	77	3.23	78	7.39	302.5
14	Shane Bieber S. Bieber	3.24	883.1	143	66	34	.660	141	995	5	2	0	786	318	339	102	195	19	1	1	3,574	34	10.14	1.99	5.10	1.04	27.8	5.5	1.11	.302	3.45	76	3.15	75	8.01	106.7
15	Zack Wheeler Z. Wheeler	3.28	1728.1	283	113	75	.601	283	1,820	5	3	0	1,475	630	683	166	490	76	0	14	7,086	41	9.48	2.55	3.71	0.86	25.7	6.9	1.14	.289	3.56	82	3.28	80	7.68	164.7
16	Justin Verlander J. Verlander	3.32	3561.2	554	265	158	.626	554	3,546	26	9	0	3,041	1,315	1,426	369	1,003	121	0	28	14,583	99	8.96	2.53	3.54	0.93	24.3	6.9	1.14	.280	3.60	79	3.43	81	7.68	312.1
17	Ranger Suárez R. Suárez	3.36	757.2	186	53	36	.596	118	701	2	2	4	719	283	311	68	240	22	22	7	3,176	11	8.33	2.85	2.92	0.81	22.1	7.6	1.27	.303	3.69	80	3.52	83	8.54	61.3
18	Framber Valdez F. Valdez	3.36	1080.2	188	81	52	.609	166	1,053	9	3	0	912	404	444	87	389	58	7	1	4,483	61	8.77	3.24	2.71	0.72	23.5	8.7	1.20	.285	3.70	81	3.51	84	7.60	77.8
19	Logan Webb L. Webb	3.40	1057.0	179	68	51	.571	176	986	3	2	0	1,017	399	440	74	250	36	0	4	4,331	22	8.40	2.13	3.94	0.63	22.8	5.8	1.20	.316	3.75	83	3.02	75	8.66	119.6
20	Seth Lugo S. Lugo	3.49	993.0	360	64	47	.577	123	954	1	0	16	889	385	413	122	276	37	66	18	4,098	22	8.65	2.50	3.46	1.11	23.3	6.7	1.17	.283	3.74	85	3.79	91	8.06	41
21	Walker Buehler W. Buehler	3.52	839.2	157	57	29	.663	146	846	3	1	0	718	328	362	106	251	38	3	4	3,467	22	9.07	2.69	3.37	1.14	24.4	7.2	1.15	.275	3.88	85	3.82	90	7.70	39.1
22	Luis Castillo L. Castillo	3.55	1410.2	243	83	84	.497	243	1,493	1	0	0	1,208	557	608	174	453	48	0	8	5,824	19	9.53	2.89	3.30	1.11	25.6	7.8	1.18	.283	3.88	86	3.72	88	7.71	78.1
23	Logan Gilbert L. Gilbert	3.58	830.1	145	46	36	.561	145	879	2	1	0	699	330	350	110	180	25	0	6	3,358	41	9.53	1.95	4.88	1.19	26.2	5.4	1.06	.272	3.79	92	3.51	88	7.58	44.5
24	Sonny Gray S. Gray	3.58	1918.0	339	125	102	.551	330	1,925	7	5	0	1,675	763	836	192	621	57	2	5	7,952	106	9.03	2.91	3.10	0.90	24.2	7.8	1.20	.288	3.92	87	3.51	85	7.86	136.3
25	Zac Gallen Z. Gallen	3.58	1007.1	176	66	51	.564	176	1,060	2	2	0	843	401	425	117	324	36	0	3	4,142	33	9.47	2.89	3.27	1.05	25.6	7.8	1.16	.279	3.80	84	3.65	89	7.53	49.1