http://www.swissdelphicenter.ch/torry/showcode.php?id=969

How to get the CPU usage in percent

const

 SystemBasicInformation = 0;

 SystemPerformanceInformation = 2;

 SystemTimeInformation = 3;

type

 TPDWord = ^DWORD;

 TSystem_Basic_Information = packed record

   dwUnknown1: DWORD;

   uKeMaximumIncrement: ULONG;

   uPageSize: ULONG;

   uMmNumberOfPhysicalPages: ULONG;

   uMmLowestPhysicalPage: ULONG;

   uMmHighestPhysicalPage: ULONG;

   uAllocationGranularity: ULONG;

   pLowestUserAddress: Pointer;

   pMmHighestUserAddress: Pointer;

   uKeActiveProcessors: ULONG;

   bKeNumberProcessors: byte;

   bUnknown2: byte;

   wUnknown3: word;

 end;

type

 TSystem_Performance_Information = packed record

   liIdleTime: LARGE_INTEGER; {LARGE_INTEGER}

   dwSpare: array[0..75] of DWORD;

 end;

type

 TSystem_Time_Information = packed record

   liKeBootTime: LARGE_INTEGER;

   liKeSystemTime: LARGE_INTEGER;

   liExpTimeZoneBias: LARGE_INTEGER;

   uCurrentTimeZoneId: ULONG;

   dwReserved: DWORD;

 end;

var

 NtQuerySystemInformation: function(infoClass: DWORD;

   buffer: Pointer;

   bufSize: DWORD;

   returnSize: TPDword): DWORD; stdcall = nil;

 liOldIdleTime: LARGE_INTEGER = ();

 liOldSystemTime: LARGE_INTEGER = ();

function Li2Double(x: LARGE_INTEGER): Double;

begin

 Result := x.HighPart * 4.294967296E9 + x.LowPart

end;

procedure GetCPUUsage;

var

 SysBaseInfo: TSystem_Basic_Information;

 SysPerfInfo: TSystem_Performance_Information;

 SysTimeInfo: TSystem_Time_Information;

 status: Longint; {long}

 dbSystemTime: Double;

 dbIdleTime: Double;

 bLoopAborted : boolean;

begin

 if @NtQuerySystemInformation = nil then

   NtQuerySystemInformation := GetProcAddress(GetModuleHandle('ntdll.dll'),

     'NtQuerySystemInformation');

 // get number of processors in the system

 status := NtQuerySystemInformation(SystemBasicInformation, @SysBaseInfo, SizeOf(SysBaseInfo), nil);

 if status <> 0 then Exit;

 // Show some information

 with SysBaseInfo do

 begin

     ShowMessage(

     Format('uKeMaximumIncrement: %d'#13'uPageSize: %d'#13+

     'uMmNumberOfPhysicalPages: %d'+#13+'uMmLowestPhysicalPage: %d'+#13+

     'uMmHighestPhysicalPage: %d'+#13+'uAllocationGranularity: %d'#13+

     'uKeActiveProcessors: %d'#13'bKeNumberProcessors: %d',

     [uKeMaximumIncrement, uPageSize, uMmNumberOfPhysicalPages,

     uMmLowestPhysicalPage, uMmHighestPhysicalPage, uAllocationGranularity,

     uKeActiveProcessors, bKeNumberProcessors]));

 end;

 bLoopAborted := False;

 while not bLoopAborted do

 begin

   // get new system time

   status := NtQuerySystemInformation(SystemTimeInformation, @SysTimeInfo, SizeOf(SysTimeInfo), 0);

   if status <> 0 then Exit;

   // get new CPU's idle time

   status := NtQuerySystemInformation(SystemPerformanceInformation, @SysPerfInfo, SizeOf(SysPerfInfo), nil);

   if status <> 0 then Exit;

   // if it's a first call - skip it

   if (liOldIdleTime.QuadPart <> 0) then

   begin

     // CurrentValue = NewValue - OldValue

     dbIdleTime := Li2Double(SysPerfInfo.liIdleTime) - Li2Double(liOldIdleTime);

     dbSystemTime := Li2Double(SysTimeInfo.liKeSystemTime) - Li2Double(liOldSystemTime);

     // CurrentCpuIdle = IdleTime / SystemTime

     dbIdleTime := dbIdleTime / dbSystemTime;

     // CurrentCpuUsage% = 100 - (CurrentCpuIdle * 100) / NumberOfProcessors

     dbIdleTime := 100.0 - dbIdleTime * 100.0 / SysBaseInfo.bKeNumberProcessors + 0.5;

     // Show Percentage

     Form1.Label1.Caption := FormatFloat('CPU Usage: 0.0 %',dbIdleTime);

     Application.ProcessMessages;

     // Abort if user pressed ESC or Application is terminated

     bLoopAborted := (GetKeyState(VK_ESCAPE) and 128 = 128) or Application.Terminated;

   end;

   // store new CPU's idle and system time

   liOldIdleTime := SysPerfInfo.liIdleTime;

   liOldSystemTime := SysTimeInfo.liKeSystemTime;

   // wait one second

   Sleep(1000);

 end;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

 GetCPUUsage

end;