JJ Montalban

This plugin create a new option in product data box of product edit page. 
You can to set a minimum, a maximum one or a quantity range for products in Woocommerce. Customers can only buy in multiplications of your defined range.

Product Quantity Settings

Define a minimum / maximum / range quantity for products on product pages & cart.

wpgear

The plugin makes it possible to sell Products as whole or in parts: 0.5 1.5 etc. 
(Piece of Product). Min, Max, Step & Default preset Quantity. Variable Products Supported.
For example: 
 Pizza. You can sell 1.5 Pizzas, or a quarter. With the price set for 1 piece. 
 Liquids on tap. For example, Kerosene or Olive Oil. You can sell 1.5 liters, with the price set for 1 liter. 
 Bulk materials. For example, Tobacco or Golden Sand. You can sell 0.1 g at a price quoted for 1 g.
<h4>Futured</h4>
<ul>
<li>You can set the Minimum product Quantity for all Products by default (preset = 1). But at the same time, each Product / Categories can have its own Minimum Quantity value.</li>
<li>You can set the Step of Changing the Quantity of goods for all Products by default (preset = 1). But at the same time, each Product / Categories can have its own value for the Change in Quantity Step.</li>
<li>You can set the Default – Choice product quantity for all Products by default (preset = 1). But at the same time, each Product / Categories can have its own Default – Choice Quantity value. </li>
<li>You can set the Maximum product Quantity for all Products by default. But at the same time, each Product / Categories can have its own Maximum Quantity value.</li>
<li>Works correctly with Variable Products.</li>
<li>Auto correction “No valid value” customer enters to nearest valid value.</li>
<li>Auto correction considering with “Maximum allowed for Product”.</li>
<li>Column “Quantity” on Products List.</li>
<li>Update Cart Automatically on Quantity Change (AJAX Cart Update)</li>
<li>You can set a “Value Label” for each individual Item. Individually or as a whole for the Category. For example: “Price per Meter”, “Price per Liter”.</li>
<li>It is possible to use Product – JS Object for Ext.Integration: QNT_Data. Function: WDPQ_Get_QuantityData (Product_ID).</li>
<li>Works with WooCommerce specifics from v3.4.8 & more</li>
<li>
Buttons: +/- To select the Quantity on the Product page and in the Cart.
<a href="http://wpgear.xyz/decimal-product-quantity-woo-pro/" rel="nofollow ugc">PRO Version</a> Features:
</li>
<li>You can set separate Minimum Product Quantity, Step of Changing the Quantity & Default preset Quantity – for each Variable Product Variation.</li>
<li>You can create RSS Feed for WooCommerce. Support: “Google Merchant Center” (Product data specification) for “Price_Unit_Label” -> [unit_pricing_measure], separate hierarchy Categories -> Products.</li>
</ul>

Decimal Product Quantity for WooCommerce

Products like: Pizza, Liquid on the filling, Custom weight, etc. (Piece of Product). Min, Max, Step & Default preset Quantity. Variable Supported.

Product Quantity Settings vs Decimal Product Quantity for WooCommerce