Here is how you can add WooCommerce add to cart button and quantity field/form to Shop archive page. You may have just a bunch of linked products on the shop page but want to add a quicker way for a customer to add products to cart.

Woocommerce Shop Page No Add To Cart

No add to cart button

 

Depending on your WordPress theme the add to cart button may or may not be there – if not add the add to cart button use the code below in your functions.php file…

add_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_loop_add_to_cart' );

For the quantity field use…

add_filter( 'woocommerce_loop_add_to_cart_link', 'quantity_inputs_for_woocommerce_loop_add_to_cart_link', 10, 2 );
/**
 * Override loop template and show quantities next to add to cart buttons
 * @link https://gist.github.com/mikejolley/2793710
 */
function quantity_inputs_for_woocommerce_loop_add_to_cart_link( $html, $product ) {
	if ( is_user_logged_in() && is_shop() && $product && $product->is_type( 'simple' ) && $product->is_purchasable() && $product->is_in_stock() && ! $product->is_sold_individually() ) {
		$html = '<form action="' . esc_url( $product->add_to_cart_url() ) . '" class="cart" method="post" enctype="multipart/form-data">';
		$html .= woocommerce_quantity_input( array(), $product, false );
		$html .= '<button type="submit" class="button alt">' . esc_html( $product->add_to_cart_text() ) . '</button>';
		$html .= '</form>';
	}
	return $html;
}

This will give us…

Woocommerce Shop Page With Add To Cart Quantity

Now there is the quantity and add to cart

The button and quantity are on the page but need a little CSS this will vary depending on your theme…

.product .cart {
	display: flex;
	flex-flow: row nowrap;
	justify-content: center;
	margin-top: 10px;
}

.product .cart button[type="submit"] {
    margin: 0 10px !important;
}

Giving us….

Woocommerce Shop Page With Add To Cart Aligned

Button and quantity are aligned

Finally to keep the customer on the shop page so they can continually add products to cart – ensure the ‘Add to cart behaviour’ has the ‘Enable AJAX add to cart buttons on archives ‘ checked and the redirect to cart unchecked.

Add To Cart Ajax

 

Product Category Archive Pages

To include the quantity box on product category pages, you need to include the option of them in the first snippet, so as below…

add_filter( 'woocommerce_loop_add_to_cart_link', 'quantity_inputs_for_woocommerce_loop_add_to_cart_link', 10, 2 );
/**
 * Override loop template and show quantities next to add to cart buttons
 * @link https://gist.github.com/mikejolley/2793710
 */
function quantity_inputs_for_woocommerce_loop_add_to_cart_link( $html, $product ) {
	if ( is_user_logged_in() && is_shop() || is_product_category() && $product && $product->is_type( 'simple' ) && $product->is_purchasable() && $product->is_in_stock() && ! $product->is_sold_individually() ) {
		$html = '<form action="' . esc_url( $product->add_to_cart_url() ) . '" class="cart" method="post" enctype="multipart/form-data">';
		$html .= woocommerce_quantity_input( array(), $product, false );
		$html .= '<button type="submit" class="button alt">' . esc_html( $product->add_to_cart_text() ) . '</button>';
		$html .= '</form>';
	}
	return $html;
}

The only difference is || is_product_category() is added.