Fixed vs. Variable Costs: The 20-Minute Audit Every Owner Should Run Quarterly

Understanding the difference between fixed and variable costs is one of the fastest ways to gain real control over your business's financial flexibility, and it takes far less time than most owners assume. Here's a simple 20-minute exercise worth running every quarter.

Fixed costs are expenses that stay roughly the same regardless of how much you sell: rent, salaries, insurance, software subscriptions, loan payments. Variable costs rise and fall directly with your business activity: materials, hourly labor tied to specific jobs, shipping, payment processing fees. Understanding which of your costs fall into each category tells you two critical things: how much revenue you need just to break even, and how much flexibility you have if revenue slows down.

Start the audit by pulling your last full month of expenses. Go through them one by one and sort each into fixed or variable. Some will be obvious. Others, like a marketing budget that's technically adjustable but rarely gets adjusted in practice, deserve honest classification rather than a technical one. If you wouldn't actually cut it in a slow month, it's functioning as a fixed cost, whatever the textbook definition says.

Once sorted, add up your total fixed costs for the month. That number is your baseline: the minimum revenue you need just to keep the lights on before you make a single dollar of profit. Most owners have never calculated this directly, and seeing it in one clear number is often the most clarifying part of the whole exercise.

Next, look at your variable costs as a percentage of revenue. This tells you your true margin on each additional dollar of sales, which is different from your overall profit margin and often more useful for pricing and growth decisions.

Now ask a few honest questions. If revenue dropped 20 percent next quarter, which fixed costs could actually flex, and which are truly locked in? Are there variable costs creeping up as a percentage of revenue that deserve a closer look, like rising shipping fees or payment processing rates? Is there a fixed cost that's stopped earning its keep, a subscription nobody uses, a lease that's oversized for current needs?

Running this exercise quarterly does two things. It keeps you honest about your real break-even point as your business changes, and it surfaces waste before it becomes a bigger problem, rather than after a slow quarter forces a panic-driven cost review.

This is a genuinely simple exercise, but very few business owners run it consistently, mostly because nobody ever showed them how, not because it's difficult.

Book a free consultation with ReVamp Accounting and we'll walk through this exercise with your actual numbers and show you what it reveals.