Arpad E. Elo's
Win Percentage Expectancies
From Rating Differences.

H: % of games to win by higher rated player
L: % of games to lose by lower rated player

Rating Diff	H	L	Rating Diff	H	L	Rating Diff	H	L	Rating Diff	H	L
000-003	50	50	092-098	63	37	198-206	76	24	345-357	89	11
004-010	51	49	099-106	64	36	207-215	77	23	358-374	90	10
011-017	52	48	107-113	65	35	216-225	78	22	375-391	91	09
018-025	53	47	114-121	66	34	226-235	79	21	392-411	92	08
026-032	54	46	122-129	67	33	236-245	80	20	412-432	93	07
033-039	55	45	130-137	68	32	246-256	81	19	433-456	94	06
040-046	56	44	138-145	69	31	257-267	82	18	457-484	95	05
047-053	57	43	146-153	70	30	268-278	83	17	485-517	96	04
054-061	58	42	154-162	71	29	279-290	84	16	518-559	97	03
062-068	59	41	163-170	72	28	291-302	85	15	560-619	98	02
069-076	60	40	171-179	73	27	303-315	86	14	620-735	99	01
077-083	61	39	180-188	74	26	316-328	87	13	over-735	100	00
084-091	62	38	189-197	75	25	329-344	88	12

Dr. Elo's writ explaining in full his statistical rating system will be available here soon.