Form action Add to Cart Product URL in Magento

Solution 1:

$_productId = '166';
$_product = Mage::getModel('catalog/product')->load($_productId);
$_url = $this->getSubmitUrl($_product);

Solution 2:

$_productId = '166';
$_product = Mage::getModel('catalog/product')->load($_productId);
$_url = Mage::helper('checkout/cart')->getAddUrl($_product);