---
title: "Contribution Margin vs Gross Margin for Online Stores"
description: "Gross margin ignores variable selling costs. Contribution margin includes fees, shipping, and often ads—making it the better lever for ecommerce decisions."
date: 2026-01-12
updated: 2026-01-12
author: CostRadar Editorial
tags: [contribution-margin, gross-margin, definitions]
heroKeyword: contribution margin ecommerce
draft: false
---

Gross margin tells you product economics. Contribution margin tells you whether an order, SKU, or channel covers the variable costs of selling it. Confusing the two is one of the most expensive mistakes in ecommerce finance.

## Definitions side by side

**Gross margin** = Net sales − COGS.

**Contribution margin** = Net sales − COGS − variable selling costs (payment fees, marketplace fees, shipping, pick/pack, and typically performance ads attributable to the sale).

Contribution margin is the amount left to cover fixed costs and profit. A 55% gross margin SKU can have a 5% contribution margin after Amazon fees and Meta ads.

## When to use each metric

Use gross margin for supplier negotiations and product design. Use contribution margin for pricing, channel mix, ad bids, and kill/keep SKU decisions.

Finance teams that only report gross margin systematically approve ad budgets that destroy contribution.

## Practical checklist

List every variable cost that moves with an order. Attribute ads carefully (last-click is imperfect but better than zero). Recalculate contribution margin when fee schedules or freight rates change.

## FAQ

**Are apps fixed or variable costs?**

Most SaaS apps are fixed (or step-fixed) monthly costs. Attribute them in true net profit; usually exclude them from per-order contribution margin unless priced per order.

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CostRadar helps merchants track the fee and ad layers that turn healthy gross margin into thin contribution margin.