A quick note before you read: This guide is general education only—not financial, tax, or legal advice. Your numbers and the right decisions for your business depend on your specific situation. Use these as starting-point guidelines, and consult a qualified accountant before making important financial decisions.
Setting a price is one thing; knowing whether that price actually makes you money is another. This guide is about the second part—the margin and break-even math that tells you how healthy each sale really is. (If you’re still deciding what to charge, start with the pricing basics guide first, then come back here to check the math.)
Revenue isn’t profit
It’s easy to feel good about a big sales number and miss that very little of it is actually yours to keep. The chain looks like this: revenue comes in, the cost of delivering goes out, and what’s left has to cover your overhead before anything counts as profit. A business doing impressive revenue with thin margins can be far weaker than a smaller one with healthy ones. Margin is what matters.
Gross margin: the money left to run on
Gross margin is the percentage of each sale left after the direct cost of delivering it (your cost of goods sold).
Gross margin = (Price − Cost to deliver) ÷ Price
So if you sell something for $100 and it costs you $40 to deliver, your gross margin is 60%. That 60% is what’s available to cover everything else—rent, marketing, software, your own pay—and ultimately to become profit. The higher your margin, the more room you have to operate, invest, and absorb surprises.
Contribution margin: what each extra sale adds
Contribution margin is what one additional sale contributes toward covering your fixed costs, after its own variable costs. Early on, this is the number that tells you whether selling more actually helps. If each sale contributes meaningfully after its direct costs, growth strengthens you. If each sale barely contributes—or contributes nothing—selling more just creates more work without building the business.
Break-even: how many sales until you’re in the black
Your break-even point is the level of sales where total income exactly covers total costs—the point past which you start making money. The simple version:
Break-even units = Fixed costs ÷ Contribution margin per unit
If your fixed monthly costs are $3,000 and each sale contributes $30 after its variable costs, you need 100 sales a month to break even. Everything above that is profit; everything below is a loss you’re funding from your cushion. The free Milk Spider finance toolkit includes a break-even calculator that runs this math for you.
Free download: Milk Spider Finance Toolkit (Excel) — includes a break-even calculator plus a 13-week cash-flow forecast.
Knowing this number is clarifying. It turns a vague "I hope this works" into a concrete target: this many sales a month and I’m sustainable. It also tells you instantly whether a price is viable—if hitting break-even requires more customers than realistically exist, the price (or the cost structure) needs to change.
Use the math to make decisions
Once you know your margins and break-even, a lot of decisions get easier:
- Should I cut my price to compete? Only if you can hit break-even at the higher volume a lower price requires. Often you can’t.
- Should I take on this cost? Check how many extra sales it forces you to make to stay in the black.
- Where should I focus? Higher-margin offers move you toward profit faster than higher-revenue, low-margin ones.
Keep your costs honest
The math only works if you count all your costs—including the ones that are easy to forget: payment processing fees, your own time, software, returns, and the slice of overhead each sale should carry. Underestimating costs makes margins look healthier than they are, which leads to prices that quietly lose money. When in doubt, count more carefully, and have an accountant sanity-check your numbers.
FAQ
What’s the difference between gross margin and profit?
Gross margin is what’s left after the direct cost of delivering a sale. Profit is what’s left after everything, including fixed costs like rent and overhead. Healthy gross margin makes profit possible, but it isn’t profit by itself.
What’s a "good" margin?
It varies enormously by industry—a software business and a restaurant live in different worlds. Compare yourself to similar businesses, and focus on improving your own margin over time. An accountant can help you benchmark.
How does break-even help me set prices?
It tells you how many sales each possible price requires. If a price forces you to sell more than is realistic, that price won’t work—no matter how attractive it looks.
Why include my own time as a cost?
Because your time is real and finite. A "profitable" business that only works because you’re unpaid isn’t actually profitable—it’s a job that’s losing money. Counting your time keeps you honest about whether the model truly works.