Hi Beautyworld ,
Thank you very much for your post and question.
I am not trying to push you our premium feature, but the only way to achieve this in WooCommerce is by using the Product Levels premium add-on.
You can scroll down on that page to try a demo.
Your setup:
Raw Material: "Finished Goods" - you can either stock them by packs of 1 x 100 or simply by creating the stock of 100.
In your product - go to the bill of materials section and associate it with the raw material. If your product contains 10 items from the pack:
- add 10 into the association field if you stock your raw material as 100
- add 0.1 into your association field if you stock your raw material as 1 ( so one item means one pack of 100).
They when you sell a product the raw material will deduct its stock accordingly.
Hope this makes sense.
Pavel