Free tool
Gross margin is not contribution margin.
Gross margin stops at COGS. Contribution keeps going. If you manage to gross margin you will scale ads into a hole.
Gross margin$77.00 (64.16%)
Contribution margin$46.00 (38.33%)
Formula
gross_margin = (sale − cogs) / sale; contribution_margin = contribution / sale
Example
$120 sale, $43 COGS is 64% gross. After $18 + $4 + $9 fees and ship, contribution is $46 — 38%.