ROAS, return on ad spend, is revenue attributed to ads divided by the ad spend that produced it. A ROAS of 4x means every ad dollar returned four dollars of revenue.
Revenue is not profit. The breakeven line in this calculator uses your gross margin to show the ROAS you need just to cover costs: breakeven ROAS equals 100 divided by gross margin percent. A business with 40% margins breaks even at 2.5x, so a 3x campaign is profitable and a 2x campaign loses money, even though both sound healthy.
The 412 Freelancers ROAS calculator also shows profit after ad spend when revenue, spend, and margin are all entered, which is the number the campaign should actually be judged on.