WooCommerce Quantity Manager 

This is a GPL-distributed version. No official support. Clean, secure, and legally redistributed under the GPL license.

Min/Max Quantity Value
Set minimum and maximum quantities and spend amounts before the customer can checkout and complete their order.

Quantity Step Values
Add interval-based quantities and multiples. Customers must purchase in the required quantity groupings.

Change the Default Quantity
Subtly encourage customers to buy more by changing the initial starting value in the quantity field for each product.

Fine-Grained Control
Set quantity rules globally for the entire order, or per category, product or even individual product variations.

Helpful Errors Prompts
The plugin validates and gently guides customers to add the correct quantity so that they can proceed to the checkout.

Super-Fast Setup
WooCommerce Quantity Manager is easy and intuitive to use – ideal for both beginners and developers.