We can use the below code to retrieve product Review/Rating summary in Magento
<?php
$product = Mage::getModel('catalog/product')->load($productId);
$storeId = Mage::app()->getStore()->getId();
$summaryReview = Mage::getModel('review/review_summary')
->setStoreId($storeId)
->load('product_id');
if($summaryReview->getRatingSummary()){
?>
<div class="rating-box" style="float:left;">
<div class="rating" style="width: <?php echo $summaryData->getRatingSummary().'%'; ?>">
</div>
</div>
<?php
}
?>
