You did not mention your platform. vmstat reports (amongst other things) percentages of total CPU time:

• us: Time spent running non-kernel code. (user time, including nice time)
• sy: Time spent running kernel code. (system time)
• id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
• wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.

$ vmstat -n 1
procs -----------memory---------- ---swap-- -----io---- --system-- ---
+-cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us 
+sy id wa
 1  0    160  84600 330848 251724    0    0    74   102    1     0  8 
+ 2 90  0
 0  0    160  84600 330848 251724    0    0     0     0 1018   337  1 
+ 0 99  0
 0  0    160  84600 330848 251724    0    0     0   160 1011   343  3 
+ 0 97  0
 0  0    160  84600 330848 251724    0    0     0     0 1019   351  1 
+ 0 99  0
 0  0    160  84608 330848 251724    0    0     0     0 1003   344  2 
+ 0 98  0
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