Ask most business owners which of their products is doing best, and they'll name whatever sells the most units. That's a natural answer. It's also often wrong.
Best-selling is not the same as most profitable.
A simple example
- Sells 500 units a month
- Thin margin per unit
- Looks like the clear winner by volume
- Sells only 100 units a month
- Much stronger margin per unit
- Can contribute more total profit than Product A
Whether A or B actually contributes more to the business depends entirely on the margin behind each sale — not the unit count. A product moving fast on a thin margin can contribute less real profit than a slower product with a healthier one. Without looking at margin directly, you'd never know which is which just from a sales report.
The numbers behind the question
- Unit cost — what one unit actually cost you to buy or produce.
- COGS — total cost of the units sold, not just one.
- Gross profit — revenue from that product minus its COGS.
- Gross margin — gross profit as a percentage of that product's revenue.
- Sales velocity — how fast it moves, which matters for cash flow but not for margin.
Why this is harder than it sounds — and where honesty matters
Getting this right requires knowing the real cost behind every unit sold, at the time it was sold — not today's cost, since supplier prices change. That's a specific, deliberate thing to track, and most small businesses don't have it consistently.
This is exactly where it's worth being precise about what a system can and can't honestly tell you. Guardian's product-profitability view, for sales recorded through Run/Sell, is built around historical cost snapshots — the cost of a product is captured at the moment it's sold, not pulled from today's price list. That matters, because if a supplier raises prices next month, it shouldn't quietly rewrite what last month's sales actually earned.
If a sale doesn't have a known cost behind it, that sale is left out of the profit number — never counted as if it cost nothing.
That distinction is deliberate and important. A product added to the system without a recorded cost — which happens, especially early on — produces sales with no cost data attached. Guardian excludes those specific sales from the gross-profit calculation rather than treating missing cost as zero cost, because a confidently wrong number is more dangerous than an honestly incomplete one. Alongside any profit figure, Guardian shows what share of revenue in the period actually had known cost behind it — so you always know how complete the picture is, not just what the number says.
This is a genuinely different posture from a system that just wants to show you an impressive-looking number. Guardian doesn't ask "how much did you sell?" and stop there — it asks what the activity actually tells you, and says plainly when it doesn't yet have enough to say for sure.
Find out what your sales data is actually telling you →
Getting the cost data in
The more consistently product costs are recorded as you go — when you add a product, when a purchase comes in — the more complete this picture becomes. It's not a one-time setup; it's an ongoing habit that pays off directly in how much Guardian can tell you.
Guardian is built to make this kind of margin-level visibility accessible without a dedicated analyst or a spreadsheet you have to maintain yourself, backed by a 30-day money-back guarantee if it doesn't surface something meaningful from your evidence in the first month.
Who this is for
If you don't yet record product costs at all, that's the place to start — even rough costs recorded consistently beat none. If you're already tracking costs and want to know, honestly, which products are really contributing — not just which ones are popular — this is exactly the question Guardian is built to help answer.