I can't take credit for this, it was posted somewhere here some years ago and I bookmarked it because I thought it was really encouraging. It cheered me up and made me realise I am not doing so bad for a 61 year old as I thought I was so I thought it worthy of a repost:
Column 1 is age, Col 2 is the age-graded (adjusted) time of a 5k run in 30mins, Col 3 is the actual time you should be aiming for to achieve an age-graded equivalent 30 min 5k.
Women:
20 - 0:29:59 - 0:30:01
25 - 0:30:00 - 0:30:00
30 - 0:29:59 - 0:30:01
35 - 0:29:41 - 0:30:19
40 - 0:28:58 - 0:31:05
45 - 0:27:48 - 0:32:23
50 - 0:26:14 - 0:34:18
55 - 0:24:36 - 0:36:35
60 - 0:22:58 - 0:39:11
65 - 0:21:20 - 0:42:11
70 - 0:19:42 - 0:45:41
Men:
20 - 0:29:41 - 0:29:41
25 - 0:30:00 - 0:30:00
30 - 0:29:56 - 0:30:05
35 - 0:29:22 - 0:30:39
40 - 0:28:21 - 0:31:45
45 - 0:27:18 - 0:32:58
50 - 0:26:14 - 0:34:18
55 - 0:25:11 - 0:35:44
60 - 0:24:08 - 0:37:18
65 - 0:23:04 - 0:39:00
70 - 0:21:57 - 0:41:00