Return on ad spend (ROAS)
How much revenue each pound of ad spend brings back, compared with break-even at your profit margin.
The formula
ROAS = Revenue ÷ Ad spend · Break-even ROAS = 1 ÷ Margin
How to read it
If ROAS is above break-even, each extra pound of spend earns money. If it's below, raise margin or improve conversion before raising the budget.