$filename = 'D:\PS\CSV\PowerShell-EventLogs.csv'    

# Get file size in bytes
(Get-Item -Path $filename).Length

# get file size in KB in PowerShell
(Get-Item -Path $filename).Length/1KB

# get file size in MB in PowerShell   
(Get-Item -Path $filename).Length/1MB

# get file size in GB in PowerShell
(Get-Item -Path $filename).Length/1GB