Get rating product by product id

Given a product ID you can get the average rating like this:

$product = wc_get_product( $product_id );
$rating  = $product->get_average_rating();

That'll return the raw number (4.00, 3.50 etc.).

To output the rating HTML for a given product you can use this code:

$product = wc_get_product( $product_id );
$rating  = $product->get_average_rating();
$count   = $product->get_rating_count();

echo wc_get_rating_html( $rating, $count );

Or, if you're in the loop you can use this function to get the HTML for the current product:

woocommerce_template_loop_rating() 

You can fetch loop top rating product

$args_top_rating1 = array(
    'post_type' => 'product',
    'meta_key' => '_wc_average_rating',
    'orderby' => 'meta_value',
    'posts_per_page' => 8,
    'status'=>'publish',
    'catalog_visibility'=>'visible',
    'stock_status'=>'instock'
);

$top_rating = new WP_Query( $args_top_rating1 );


 while ( $top_rating->have_posts() ) : $top_rating->the_post(); global $product; 

        $urltop_rating = get_permalink($top_rating->post->ID) ;

$rating_count = $product->get_rating_count();

$average_rating = $product->get_average_rating();

echo wc_get_rating_html( $average_rating, $rating_count);  


endwhile;

This helped me a lot, create the get_star_rating () function and return your html.

NOTE: If it is in a loop

function get_star_rating() {

    global $woocommerce, $product;  

    $average      = $product->get_average_rating();
    $review_count = $product->get_review_count();

    return '<div class="star-rating">
                <span style="width:'.( ( $average / 5 ) * 100 ) . '%" title="'. 
                  $average.'">
                    <strong itemprop="ratingValue" class="rating">'.$average.'</strong> '.__( 'out of 5', 'woocommerce' ).                              
                '</span>                    
            </div>'.'
            <a href="#reviews" class="woocommerce-review-link" rel="nofollow">( ' . $review_count .' )</a>';

}