Most SME owners know their revenue. Some know their gross margin. Very few know the numbers that actually predict whether their business is healthy — or quietly heading for trouble.
Revenue tells you what came in. Gross margin tells you what's left after direct costs. Both are important. But neither tells you whether your growth is profitable, whether your cash will hold up, whether your customers are staying, or whether the productivity of your team is improving or declining. For that, you need five more numbers.
These five cut across finance, operations, sales, and customer success. Together, they give you a complete picture of business health in under five minutes. Most SME owners either don't calculate them at all, or calculate them once and never review them again. That's the gap this article is designed to close.
1. Gross Margin by Product or Service Line
Overall gross margin is a start, but it hides critical information. When you average across every product or service you sell, the profitable lines subsidise the unprofitable ones — and you can't see it happening.
The number you actually need is gross margin broken out by product line, service type, or client category. This tells you which parts of your business are pulling their weight and which are quietly dragging on profitability.
In practice, this often produces surprises. A professional services firm that does both retained monthly work and one-off projects will frequently find the projects carry much lower margins once delivery time is accounted for. A product business might find that its highest-revenue line is barely covering its cost of goods. Neither of these problems is visible in the blended margin figure.
The benchmark varies enormously by industry — software businesses might target 70%+, services businesses 40-60%, product businesses 30-50%. What matters is knowing your number by line, not just the average. If you're pricing without knowing this, you're guessing.
2. Customer Acquisition Cost vs. Customer Lifetime Value
Customer Acquisition Cost (CAC) is the total amount you spend to win a new customer — marketing, sales effort, time, tools — divided by the number of new customers won in that period. Customer Lifetime Value (LTV) is how much a customer spends with you over the full duration of their relationship with your business.
The ratio between them — LTV:CAC — tells you whether your growth model is sustainable. A healthy ratio is generally considered to be 3:1 or better: for every £1 you spend acquiring a customer, you should expect to earn at least £3 back. A ratio below 1:1 means you're losing money on growth. A ratio above 5:1 might mean you're under-investing in acquisition and leaving revenue on the table.
Most SMEs have never formally calculated either number. They have a vague sense that marketing "costs money" and that customers "spend a fair bit." That vagueness is expensive. When you calculate the ratio, you know exactly how hard you can afford to chase new customers — and whether your retention is good enough to make acquisition worthwhile.
3. Cash Conversion Cycle
A business can be profitable on paper and still run out of cash. This is one of the most common causes of SME failure, and it's entirely predictable if you're watching the right number.
The cash conversion cycle measures how long it takes from spending money — on stock, staff, materials, or services — to receiving money from a customer. The shorter it is, the healthier your cash position. The longer it is, the more working capital you need to keep the business running.
For product businesses: it's the time from paying for stock to collecting payment from the sale. For services businesses: it's the time from incurring delivery costs (staff time, subcontractors) to the invoice being paid. A 90-day cash conversion cycle means you're funding three months of costs before you see a return. That's a significant working capital burden — and if you're growing, it gets worse before it gets better.
Actions that shorten the cycle: faster invoicing after delivery, shorter payment terms, deposits or retainers upfront, better credit control processes. All of them free up cash without requiring a bank facility or external investment. But you can only optimise what you're measuring.
4. Revenue Per Employee (or Revenue Per Billable Hour)
This is the simplest proxy for business productivity and efficiency, and it's one of the most overlooked. Total revenue divided by headcount gives you revenue per employee. For service businesses that bill by time, revenue divided by total billable hours available is even more precise.
What you're looking for is the trend. If revenue per employee is rising over time, you're becoming more efficient — the same number of people are generating more output. If it's flat or declining, something is wrong: you may be over-staffed relative to your revenue base, pricing may have slipped, utilisation may be poor, or you may have added headcount ahead of the revenue that was supposed to follow.
This metric is also useful for benchmarking decisions. If a competitor is generating £200k revenue per employee and you're at £120k, that's a significant efficiency gap — and it's worth understanding why before you hire again.
Trending up means you're becoming more efficient. Trending down means something's wrong — and you need to know which of utilisation, pricing, or headcount is the culprit.
5. Churn Rate (or Repeat Purchase Rate)
For subscription or retainer businesses: churn rate is the percentage of customers or revenue you lose in a given period. If you start a month with 100 clients and end with 94, your monthly churn is 6%. That might sound manageable. Annualised, it's 72% — meaning you need to replace nearly three-quarters of your customer base every year just to stay flat.
For project or transaction businesses: repeat purchase rate is the equivalent number. What percentage of clients from last year bought again this year? A high rate means you're building something durable. A low rate means you're on a treadmill — constantly spending on acquisition to replace revenue that isn't coming back.
Churn is the number that determines whether you're building equity in your customer base or just renting it. It's also one of the most actionable metrics in the business: it forces you to ask which clients are leaving, why, and at what point in the relationship the relationship starts to deteriorate.
What to Do If You Can't Calculate These Numbers
If you tried to work through these five numbers and found that the data isn't available, isn't clean, or is scattered across systems that don't talk to each other — that's important information. It's not a business problem, it's a data infrastructure problem. And it's one of the most common findings when SMEs do an honest assessment of their BI maturity.
The inability to calculate a number you need is a signal that something in your data foundation needs attention: how data is collected, where it lives, how it's structured. That's fixable — but only if you know it's broken.
The free BI Baseline Score assesses your data foundation across five dimensions and tells you exactly where your gaps are. The KPI Starter Pack included with BI Without the BS gives you the formulas and definitions for all 30 foundational SME KPIs — including all five covered here — so you have a clear specification for what you need to be able to calculate.
The Broader Point
Knowing these five numbers isn't about being a data analyst. It's about being a competent business owner. The businesses that get into trouble are almost always ones where the fundamentals were deteriorating for months before anyone noticed — because nobody was watching the right indicators.
These five numbers won't run your business for you. But they will tell you, quickly and reliably, whether it's heading in the right direction.