Paste a product page URL. This grades it against a 12-point rubric built for someone who’s never heard of the brand and just clicked a Meta ad. It then works out what conversion rate that grade actually buys you, against what you need to break even.
Shopify product pages work best.
One calculator rarely tells the whole story. This is the order that actually works: from margin, to target, to a page that can convert the traffic you send it.