What is a Variable Cost?

Variable costs are the expenses that move in lockstep with your sales volume or production output.

It is a simple concept that often trips up new founders when they are trying to model out their financial future. At its core, a variable cost is an expense that changes in proportion to how much you produce or sell.

If you sell zero units, your variable costs should theoretically be zero.

If you sell a million units, your variable costs will rise significantly to match that activity.

For a startup, identifying these costs early is critical. It allows you to understand the true cost of delivering your value proposition to a single customer.

Variable costs are directly tied to activity.

Think about the raw materials required to create a physical product. If you are manufacturing bicycles, the cost of the steel, rubber, and gears are variable costs. You do not buy the rubber for the tires unless you are building the bike.

Common examples include:

• Raw materials and components
• Packaging supplies
• Shipping and freight fees
• Credit card processing fees
• Commissions for sales staff
• Billable labor wages

These costs are unavoidable if you want to generate revenue. As you grow, these costs grow with you. The goal is not necessarily to eliminate them, but to manage them so they do not eat up your margin.

To fully grasp variable costs, you have to contrast them with fixed costs.

Fixed costs are the bills you pay regardless of whether you sell one item or ten thousand. These are expenses like rent, insurance, salaried payroll, and software subscriptions. They are static over a specific period.

The relationship between these two cost types determines your break-even point.

If you have high fixed costs, you need to sell a high volume of products to cover the overhead before you make a profit. If you have high variable costs, your profit on each individual item is lower, which also impacts how quickly you can cover those fixed expenses.

Startups often struggle to categorize expenses correctly here. Is a server cost fixed or variable? For a small app, it might feel fixed. For a massive platform, bandwidth usage makes it a variable cost. You need to decide how strictly you want to track these inputs based on your business model.

Investors and founders love software businesses because they typically have low variable costs.

Once the code is written, selling a copy to one user costs almost the same as selling it to a million users. This allows for massive scalability and high profit margins.

Service businesses or hardware startups face a different reality. They usually have high variable costs. To sell more services, you need more people. To sell more hardware, you need more materials.

This brings us to unit economics. This is the direct revenue and cost associated with a particular business model on a per-unit basis.

If your variable cost per unit is higher than the price you charge, you do not have a business. You have a hobby that loses money.

Founders must ask themselves difficult questions regarding these metrics.

Are there ways to reduce variable costs through bulk purchasing? Can you automate processes to remove billable labor from the equation? Do you actually know what your variable costs are, or are you guessing?

Understanding this term is not just about accounting. It is about knowing if your business can actually scale.