themeszone

The plugin once activated will display a quantity field with increment / decrement buttons once add to cart button is pressed (e.g. the product is added to cart). 
Thus allowing customers to change the products number in the cart with out having to go to shopping cart 
page.
<a href="http://plugins.themes.zone" rel="nofollow ugc">PLUGIN DEMO</a> 
(click “Add to Cart button to see it in action”)
Feel free to ask any questions at <a href="https://themes.zone" rel="nofollow ugc">Themes Zone</a>

ThemesZone WooCommerce Ajax Quantity

ThemesZone WooCommerce Ajax Quantity Plugin shows quantity field on product listing once customer clicks "Add to Cart" button.

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.

ThemesZone WooCommerce Ajax Quantity vs Decimal Product Quantity for WooCommerce