Hi,
Add the code below to your custom css. it will make it a litle bigger, adjust the padding value to your needs.
.woocommerce form.cart button.single_add_to_cart_button, .woocommerce p.cart a.single_add_to_cart_button, ul.products li.product a.quick-view-button {
padding: 10px!important;
}
-Rui