Why your average margin lies

Aiko is the AI-driven digital consultant at AIKO Node. This is the first article in a series of five, and the rest build on it. The central point is simple: the blended margin in your management accounts can look healthy while some of your customers and products lose you money. Only margin by customer and by product shows which ones.

Why the average looks fine

A blended gross margin is a weighted average. It tells you where the business ended up, not how it got there. A strong set of accounts can carry a weak set, and nothing in the headline figure says which is which.

Gary Cokins, writing in the IMA's Strategic Finance and reprinted by CustomerThink, describes this as a "profit cliff": a company "earns a substantial amount of profit from a minority of customers, roughly breaks even on some, and then loses profits on the remainder." Most owner-managed manufacturers and wholesalers have a version of that shape. Few have drawn it.

The owner usually sees one number each month. If it holds steady, there is little reason to look underneath. That is exactly why the problem lasts.

Why now: costs are moving faster than your price list

Your price list is a snapshot. Your costs are not. According to the Office for National Statistics, input prices for UK producers rose 6.1% in the year to August 2026, up from a revised 5.8% in July. Output prices rose 3.7%, up from a revised 3.3%. The ONS points to crude oil, up 26.7% on the year, as the largest upward contribution, with metals and non-metallic mineral products up 8.8%. Domestic food inputs fell 2.2%.

Two things follow. First, input costs are rising faster than factory-gate prices, which is the gap that compresses margin. Second, the movement is uneven. A product that is mostly steel and a product that is mostly food ingredients are not facing the same year. The ONS notes that July and August figures are provisional and still affected by the conflict in the Middle East.

Make UK's Manufacturing Outlook for the third quarter of 2026 points the same way. Its senior economist says rising costs "continue to put pressure on margins", and the report describes energy, employment and regulatory costs as weighing on decisions. The report page gives no figures for margins, so treat it as direction, not measurement.

Consumer inflation is a poor guide here. The ONS puts CPI at 3.1% in August 2026, up from 2.9% in July. That number describes a household basket. Your cost base is a different basket, and it is the one that matters.

What margin by customer actually means

Margin by customer is the revenue from a customer, less the cost of what you sold them, less the cost of serving them. Each part has a direct element and an allocated element.

• Direct costs: materials, labour on the job, packaging, carriage you pay for on that customer's orders.
• Allocated costs: order handling, picking, expediting, credit control, returns, account management time, and the cost of the working capital that long payment terms tie up.

The second group is where most businesses stop short. Cost allocation is a method, not an exact science, and the choices you make change the answer. Cokins's piece makes the same point about activity-based costing: it traces costs such as order fulfilment and billing to individual customers, which a product-level margin misses. The practical rule is to allocate by what causes the cost, such as the number of orders, lines picked or deliveries made, rather than spreading overhead evenly by revenue.

A worked illustration

The figures below are invented for illustration only. They are not drawn from any real business or any source.

Suppose a company sells £1,000,000 a year across four customers, with a blended gross margin of 30%, which looks respectable.

Before cost to serve, the blended margin is 30%. After it, the business keeps about £239,000 on £1,000,000 of sales, so the blended figure falls to roughly 24%. Customer D, which looks like a thin but positive account at a 22% gross margin, is losing money once frequent small orders and chasing payment are counted. Customers A and B produce £204,000 of the £239,000.

None of that was visible in the 30%. The decision it points to is also not automatic. D might be worth keeping if its terms change, or if it brings in work elsewhere. The point is that you can now choose, rather than not knowing.

How to calculate it without a new system

You do not need new software to get a first answer. A spreadsheet export and a few hours will do.

1. Export the last 12 months of sales lines: customer, product, quantity, revenue and the standard or actual cost of each line.
2. Calculate gross margin by customer. Sort from the largest customer by revenue down.
3. Pick the two or three cost-to-serve drivers that matter most in your business, for example orders per year, delivery drops and payment days beyond terms.
4. Assign a cost per driver, using a reasoned estimate from your payroll and carriage records. Record the assumption so that it can be challenged and improved.
5. Subtract the allocated cost from each customer's gross margin and compare the result with the blended average.

Expect the first pass to be rough. A rough view that is directionally right is more useful than a precise one you never build.

How this series fits together

This article gives the frame: the average hides the detail, so look at customers and products. The remaining four pieces take it further, and we suggest reading them in this order.

1. This article: why the average margin misleads.
2. The long tail: products that quietly cost you money moves from customers to products and the complexity cost of a wide range.
3. Passing on UK cost rises without losing customers uses customer margins to decide who needs a price rise and who does not.
4. Cost-to-serve: small orders and delivery terms that eat margin goes deeper on the allocated costs introduced above.
5. What a Business Health Check looks at, and what owners learn closes the series by showing how the method is applied.

What to check this month

• Pull the last 12 months of sales and calculate gross margin for your top 10 customers.
• Mark every customer whose margin is below your blended average, and any whose margin is negative.
• For those customers, estimate cost to serve using two or three drivers, and write down the assumptions.
• Compare your main material costs with the price you charge. Note which products carry the largest cost movement this year.
• Choose one account to review first, and decide what you would need to see to change terms, price or service level.

If you would like a structured view of where your own margin comes from, start with the Business Health Check.