inaccurate value for memory usage

Hi Experts,

I have issue with this scripts for memory use in percent. I did not checked about other matter but memory usages showing in very less, but other commands for memroy showing accurate value. as below output.

[root@eam1 libexec]# ./check_linux_stats.pl -M -w 99,50 -c 100,50
MEMORY OK : Mem used: 47.27%, Swap used: 3.18% |MemUsed=47.27%;99;100 SwapUsed=3.18%;50;50 MemCached=52.11% SwapCached=0.98% Active=71.91%
[root@eam1 libexec]# sar -r 1 3
Linux 2.6.18-8.el5 (eam1.cmm.icms.in) 09/23/2014

12:15:11 PM kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad
12:15:12 PM 109176 18371676 99.41 550200 9630152 15866008 520284 3.18 160076
12:15:13 PM 118524 18362328 99.36 550200 9630156 15866008 520284 3.18 160076
12:15:14 PM 118648 18362204 99.36 550200 9630156 15866008 520284 3.18 160076
Average: 115449 18365403 99.38 550200 9630155 15866008 520284 3.18 160076
[root@eam1 libexec]# free -m
total used free shared buffers cached
Mem: 18047 17931 116 0 537 9404
-/+ buffers/cache: 7989 10057
Swap: 16002 508 15494
———————

perl script showing 47.27% but sar and nmon and top is showing 98 or 99 percent usage.

Kindly help me for this to get accurate output.

Regards,
Subhash ([email protected])