Getting output as infinite or Nan

I have tried the below command to get the memory usage of the computer but getting error as infinite or NaN.

    $Totalsizemem=gwmi Win32_PhysicalMemory | Measure-Object -Property capacity -Sum | Foreach {" 
    {0:N2}" -f ([math]::round(($_.Sum / 1GB),2))}
    gwmi -computername localhost Win32_Process | Sort WorkingSetSize -Descending | Select 
    Name,@{n="Memoryusage(%)";Expression ={[math]::round(($_.WorkingSetSize / 1GB),1) / 
    $Totalsizemem*100}} | Select -First 10 | Format-Table -AutoSize | Out-Default

The expected output is -

    Name                                              Memoryusage(%)
    ----                                              --------------

    powershell_ise.exe                             0.655737704918033
    explorer.exe                                   0.655737704918033
    explorer.exe                                   0.655737704918033
    explorer.exe                                   0.655737704918033

but the output i'm getting -

    Name                 Memoryusage(%)
    ----                 --------------
    powershell_ise.exe                ∞
    svchost.exe                       ∞
    explorer.exe                    NaN
    svchost.exe                     NaN
    explorer.exe                    NaN

Does anyone know how to rectify this?

You keep rounding and formatting the intermediate results, sacrificing accuracy to the point where your data is meaningless.

Keep it simple:

$Totalsizemem = Get-WmiObject Win32_PhysicalMemory | Measure-Object -Property Capacity -Sum |Select -Expand Sum
Get-WmiObject Win32_Process |Sort WorkingSetSize -Descending |Select Name,@{Name='MemoryUsage(%)';Expression={$_.WorkingSetSize * 100 / $Totalsizemem}} -First 10