Large vhdx file when converting from vmdk

[vvatury]

Hello,
I'm using the converter tool to convert from VMDK file to VHDX using the following command:
V2V_ConverterConsole.exe convert in_file_name="C:\Server.vmdk" out_file_name="C:\Server.vhdx" out_file_type=ft_vhdx_thin
The VMDK file size is about 4gb while the output VHDX file is about 7gb, 3gb larger.
(Usually when I create the VHDX file by myself its size is the same as the VMDK file)
Can anyone please help me understand the size difference and if there's a way to solve it?

[yaroslav (staff)]

What is the original capacity of your VHD?