Financial ratios turn the raw numbers in your financial statements into a genuine diagnostic tool, telling you not just what happened but whether the business is actually getting healthier or weaker. A single ratio calculated once tells you almost nothing. Tracked monthly and compared against the previous period, the same ratio becomes an early warning system.
Here are five worth tracking, what each one actually tells you, and why the trend matters more than any single figure.
1. Net profit margin
Formula: net profit margin = net profit / sales x 100
Net profit is your total revenue minus every expense the business carries. This ratio tells you what share of every rand in sales actually reaches the bottom line. A higher margin means costs are genuinely under control relative to revenue; a margin that is shrinking while revenue grows is an early sign that costs are creeping up faster than sales, which is exactly the kind of pattern easy to miss if you only look at revenue.
2. Gross profit margin
Formula: gross profit margin = (net sales – cost of goods sold) / net sales x 100
This measures profit after subtracting only the direct cost of producing what you sold, before any operating expenses. It isolates whether your pricing and production costs are sound on their own terms, separate from how efficiently you run the rest of the business. A weak gross margin usually means a pricing or sourcing problem; a weak net margin with a healthy gross margin points instead at overheads.
3. Operating profit margin
Formula: operating profit margin = (gross profit – operating expenses) / revenue x 100
This sits between the two above: it accounts for wages and other operating costs, but excludes interest and tax, and any income unrelated to your core business activity. It is the cleanest view of what the actual operations of the business are generating, stripped of financing decisions and one-off items that can distort the bottom-line figure.
4. Working capital ratio
Formula: working capital ratio = current assets / current liabilities
Also called the current ratio, this tells you whether the business can meet its short-term obligations as they come due. A ratio of 1 or higher generally means current assets exceed current liabilities, though a very high ratio is not automatically good either, since it can signal cash sitting idle rather than being put to productive use. Watch this one particularly closely if your business has irregular income or seasonal cash flow, since it is the ratio most likely to catch a genuine cash flow problem before it becomes a crisis. Our guide to cash flow solutions for South African SMEs covers what to do if this ratio is weak.
5. Inventory turnover
Formula: inventory turnover = cost of goods sold / average inventory
Relevant mainly for retail and any business holding physical stock, this measures how many times your average inventory is sold and replaced over a period. A low turnover means capital is tied up sitting on shelves rather than generating revenue. A very high turnover can mean the opposite problem: understocking, and losing sales to customers you could not supply when they wanted to buy.
Why the trend matters more than the number
Every one of these ratios is a snapshot of a single moment. The genuine value comes from calculating them consistently, monthly is a reasonable rhythm for most small businesses, and watching the direction of travel rather than judging any single reading in isolation. A gross margin of 30% tells you very little on its own. A gross margin that has moved from 38% to 30% over six months tells you something is going wrong in pricing or cost control, and it tells you early enough to actually do something about it.
Good bookkeeping is what makes this possible in the first place: ratios calculated from incomplete or late records are worse than no ratios at all, because they create false confidence. Our bookkeeping checklist for SMEs covers the routine that keeps the underlying numbers reliable.
Frequently asked questions
How often should I calculate these financial ratios?
Monthly is a reasonable standard for most small businesses. Calculating them once and never again defeats the purpose, since the real value is in the trend rather than a single reading.
What is a good net profit margin for a small business?
It varies enormously by industry, so compare your margin against others in your specific sector rather than a generic benchmark, and more importantly, track whether your own margin is improving or declining over time.
What does a working capital ratio below 1 mean?
It suggests current liabilities exceed current assets, meaning the business may struggle to meet short-term obligations as they fall due. Treat this as an early warning to act on rather than a figure to note and forget.
Do all five ratios apply to every type of business?
Inventory turnover only applies if you hold physical stock. A service business without inventory should focus on the other four, particularly net and operating profit margin.
What is the difference between gross and net profit margin?
Gross margin looks only at the direct cost of producing what you sold. Net margin accounts for every expense the business carries. A gap between a healthy gross margin and a weak net margin points at overheads rather than pricing or production cost.
Start this month
Pull your last three months of financial statements and calculate these five ratios for each month, then look at the direction each one is moving. That single exercise, repeated monthly from here, will tell you more about the real health of the business than watching revenue alone ever will.
This article was updated in September 2026.
