How to Add Free Gift based on Selected Quantity in WooCommerce?

One popular promotional tactic similar to BOGO offers is to give an additional item for free or at a discounted rate upon purchasing a specified quantity of a product. The following code will offer two different free products based on the quantity of the product selected.

add_action('template_redirect', 'ts_add_product_to_cart');
function ts_add_product_to_cart() {
    if (!is_admin()) {
        global $woocommerce;
      
        $free_product_1_id = 470; // Replace with your free product 1 id
        $free_product_2_id = 54; // Replace with your free product 2 id
        $cart_quantity = $woocommerce->cart->cart_contents_count;

        // Remove free product 1 if already in the cart
        ts_remove_free_product($free_product_1_id);

        // Remove free product 2 if already in the cart
        ts_remove_free_product($free_product_2_id);

        // Check if cart quantity is between 3 and 6
        if ($cart_quantity >= 3 && $cart_quantity <= 6) {
            // Get the product name for Free Product 1
            $free_product_2_name = get_the_title($free_product_2_id);

             wc_add_notice("If you select beyond 6, you will get $free_product_2_name for free.", 'notice');

            // Add Free Product 1
            ts_add_free_product($free_product_1_id);
        } elseif ($cart_quantity >= 8 && $cart_quantity <= 12) {
            // Add Free Product 2
            ts_add_free_product($free_product_2_id);
        }
    }
}

function ts_add_free_product($free_product_id) {
    global $woocommerce;

    // Check if free product not already in cart
    if (!is_free_product_in_cart($free_product_id)) {
        $woocommerce->cart->add_to_cart($free_product_id);
    }
}

function ts_remove_free_product($free_product_id) {
    global $woocommerce;

    // Check if free product is in the cart
    foreach ($woocommerce->cart->get_cart() as $cart_item_key => $values) {
        $_product = $values['data'];
        if ($_product->get_id() == $free_product_id) {
            // Remove the free product
            $woocommerce->cart->remove_cart_item($cart_item_key);
        }
    }
}

function is_free_product_in_cart($free_product_id) {
    global $woocommerce;

    // Check if free product is in the cart
    foreach ($woocommerce->cart->get_cart() as $cart_item_key => $values) {
        $_product = $values['data'];
        if ($_product->get_id() == $free_product_id) {
            return true;
        }
    }

    return false;
}

Output

Based on the cart quantity of the selected product, the code adds a free product under certain conditions:

• If the cart quantity is between 3 and 6, it adds the first free product ($free_product_1_id) and also displays a notice message as shown in the image below.

If the cart quantity is between 8 and 12, it adds the second free product ($free_product_2_id).

Similarly, you can also add free products based on cart total. Look into this post that guides you well on how to automatically add a product to your WooCommerce cart based on 6 different conditions including cart total.