Hi LeahC
Thanks for consider ATUM to manage you stock 🙂
According what you are explaining, what you need is our premium add-on ATUM Product Levels. With this add-on you will be able to create BOMS (raw material or product parts) to create final products, which stock will be deducted from their BOMS.
In your case, I would do the following:
First, create the BOM. This is the quantity of product oz you have (Let's call it 'oz of total cleaning product'). The final stock will be deducted from it. You have to mark it as 'sellable', as the users will be able to buy these quantities without the packages.
Then create the final product, linking it with the BOM, so the stock of each variation will be deducted from it.
Take into account that you have to enable BOM stock control (ATUM settings > Product Levels).
Also, something you should know is that ATUM can't be 100% compatible with every plugin that exists, we have just tested the compatibility with the plugins you see on this documentation: https://forum.stockmanagementlabs.com/d/2383-atum-compatibility Said this, we can't make sure that ATUM will work properly with the Woocommerce measurement plugin.
I leave you here the documentation of the add-on where you will find useful info about how it works: https://forum.stockmanagementlabs.com/t/product-levels-documentation
And the link to the demo site in case you want to try the free trial: https://stockmanagementlabs.com/addons/atum-product-levels/
Regarding POS, we work with or own ones, and they are part of the APP we have already released (beta version). Premium users are able to test it at this moment if you are interested. Here you will find some info about POS and ATUM: https://forum.stockmanagementlabs.com/d/423-pos-and-atum
Best Regards,
Andrea.