Gross margin is the cleanest measure of how much room a product has to absorb everything else: marketing, fulfilment, returns, the cost of running the business. Once gross margin is gone, no amount of operational discipline downstream can bring it back.
Gross Margin = (Revenue - COGS) ÷ Revenue × 100
A product sold for $50 with $30 COGS has a $20 gross profit and a 40% gross margin.
Gross margin is the ceiling. Every other margin sits below it: contribution margin (after variable costs like fulfilment and payment fees), operating margin (after fixed overhead), net margin (after everything). If gross margin is 30%, no operational improvement will push net margin to 40%.
This is why gross margin discipline matters more than most merchants realise. Trimming 2 percentage points off gross margin to win a price war means trimming 2 percentage points off every margin further down the chain. A small concession at the top of the funnel becomes a large hole in net profit.
The benchmark varies. Apparel and beauty often run 60-70% gross margins. Electronics and consumer technology run 20-35%. Grocery and commodity goods run 15-25%. The right number for your business is whatever leaves enough room below it to cover variable costs, marketing, and overhead while still generating profit.
Repricing rules tied to gross margin keep automated systems honest. "Match the lowest competitor, but never below 35% gross margin" is more robust than "never below cost," because it accounts for the fact that you need more than zero profit per sale to actually run the business.
Example: A merchant analyses gross margin by category and finds electronics running at 18% versus accessories at 64%. They shift marketing spend toward accessories (where each acquired customer generates much more gross profit per order) and tighten the floor on electronics to stop losing margin in the price war.