function GetProcessMemorySize(sProcessName: string; var nMemSize: Cardinal): Boolean;
var 
  l_nWndHandle, l_nProcID, l_nTmpHandle: HWND; 
  l_pPMC: PPROCESS_MEMORY_COUNTERS; 
  l_pPMCSize: Cardinal; 
begin 
  l_nWndHandle := FindWindow(nil, PChar(sProcessName));
  if l_nWndHandle = 0 then 
  begin 
    Result := False; 
    Exit; 
  end; 
  l_pPMCSize := SizeOf(PROCESS_MEMORY_COUNTERS); 
  GetMem(l_pPMC, l_pPMCSize); 
  l_pPMC^.cb := l_pPMCSize; 
  GetWindowThreadProcessId(l_nWndHandle, @l_nProcID); 
  l_nTmpHandle := OpenProcess(PROCESS_ALL_ACCESS, False, l_nProcID);
  if (GetProcessMemoryInfo(l_nTmpHandle, l_pPMC, l_pPMCSize)) then 
    nMemSize := l_pPMC^.WorkingSetSize
  else 
    nMemSize := 0; 
  FreeMem(l_pPMC);
  CloseHandle(l_nTmpHandle);
  Result := True; 
end; 

function GetCurrentProcessMemorySize(var nMemSize: Cardinal): Boolean;
var 
  nWndHandle, nProcID, nTmpHandle: HWND;
  pPMC: PPROCESS_MEMORY_COUNTERS;
  pPMCSize: Cardinal;
begin 
  nWndHandle := Application.Handle;
  if nWndHandle = 0 then
  begin 
    Result := False; 
    Exit; 
  end; 
  pPMCSize := SizeOf(PROCESS_MEMORY_COUNTERS);
  GetMem(pPMC, pPMCSize);
  pPMC^.cb := pPMCSize;
  GetWindowThreadProcessId(nWndHandle, @nProcID);
  nTmpHandle := OpenProcess(PROCESS_ALL_ACCESS, False, nProcID);
  if (GetProcessMemoryInfo(nTmpHandle, pPMC, pPMCSize)) then
    nMemSize := pPMC^.WorkingSetSize
  else 
    nMemSize := 0; 
  FreeMem(pPMC);
  CloseHandle(nTmpHandle);
  Result := True;
end;

Get process memory usage

Delphi