How to calculate total CPU usage from SAR report?

Hi,
I want to calculate the total cpu usage from the sar report. Say for example,

Linux 2.6.24-21-generic (blade10)       09/10/2012

04:54:36 PM     CPU     %user     %nice   %system   %iowait    %steal     %idle
04:54:37 PM     all          0.00         0.00      0.00         0.00          0.00       100.00
04:54:38 PM     all          0.48         0.00      0.48         0.48           0.00        98.56
04:54:39 PM     all          0.00         0.00      0.95         0.00           0.00        99.05
04:54:40 PM     all          0.00         0.00      0.45         0.00           0.00        99.55
04:54:41 PM     all          0.46         0.00      0.91         0.00           0.00        98.63

Is it %user+%nice+%system = total CPU Usage?

Ignore the first line except the time stamp, subtract each time stamp from the prior to get seconds, convert to float (or milliseconds big integer?) and multiply by (1.0 - (% idle/100.0)) and accumulate this as the total CPU seconds used. For multiple CPU/core, multiply by the total core count.