Variable product manage stock by weight

Hello

I am creating a website where I am selling yarn by different quantity. I am trying to find a plugin to help me with my stock.

Let’s say that I have 3,5 kg or 3500 g blue yarn and I want to sell it as 100 g, 500 g and 1000 g. Lets say that I am buying 500 g and I want I want to have my stock reduce to 3,0 kg or 3000 g.

Any ideas on how to achieve this?

Madalina