ROAS is the acronym of Return on Ad Spend and is a metric in marketing that measures what is earned after taking into account the investment in advertising. It’s a form of ROI (Return on Investment) that factors in the cost of ads, by dividing the total campaign revenue by the costs of advertising activities. Let's look at an example: if an advertising campaign generates £10,000 in revenue after an investment of £2,500, the ROAS is 400%.