Formulas
Contribution per order = AOV − product cost − shipping − AOV × payment fee % − fixed fee − AOV × other % Contribution margin = contribution per order ÷ AOV ROAS = revenue ÷ ad spend Break-even ROAS = 1 ÷ contribution margin Target ROAS = 1 ÷ (contribution margin − target profit %) Profit after ads = revenue × contribution margin − ad spend
Worked example
Average order $60, product cost $24, shipping $6, payment fee 3% + $0.30. Contribution per order = 60 − 24 − 6 − 1.80 − 0.30 = $27.90, a 46.5% contribution margin. Break-even ROAS = 1 ÷ 0.465 = 2.15. To keep 15% of revenue, target ROAS = 1 ÷ (0.465 − 0.15) = 3.17. A campaign with $500 of spend and $1,800 of revenue has a ROAS of 3.6 and makes $1,800 × 0.465 − $500 = $337 after ads.
Next: the max CPC calculator turns the same numbers into the most you can bid per click.
Questions
What is break-even ROAS?
The return on ad spend at which the profit from ad-driven sales exactly pays for the ads. Break-even ROAS = 1 ÷ contribution margin. With a 46.5% contribution margin it's 2.15: every $1 of ads must bring $2.15 of revenue.
How do I calculate ROAS?
ROAS = revenue from ads ÷ ad spend. $1,800 of sales from $500 of ads is a ROAS of 3.6 (often written 3.6× or 360%).
What ROAS do I need to make a profit?
Target ROAS = 1 ÷ (contribution margin − target profit). To keep 15% of revenue as profit with a 46.5% contribution margin, you need a ROAS of 1 ÷ 0.315 = 3.17.
Why use contribution margin, not gross margin?
Because payment fees, shipping and packing are paid on every order the ads bring in. Leaving them out makes ads look more profitable than they are.