Shopify Debut Theme Code Documentation code example
Example: how to add discount code manually in shopify debut theme
{% if product.compare_at_price_max > product.price %}
{{ product.compare_at_price_max | minus: product.price | times: 100.0 | divided_by: product.compare_at_price_max | money_without_currency | times: 100 | remove: '.0'}}% off
{% endif %}