Return on ad spend, or ROAS, is a metric that measures how much you got out of the cost of your ads. You calculate ROAS by dividing your ad-attributed revenue by your ad spend. For example, if you spent $100 on an ad campaign that generated $500 of ad-attributed sales, your ROAS would be 5 ($500 divided by $100).
A higher ROAS indicates a better performance when you are measuring success based on ad-attributed sales. Keep in mind that if you are prioritizing brand awareness or repeat purchase rate, ROAS would not be the most illuminating success metric, and the ad campaign with the highest ROAS isn’t necessarily the most successful one.