Gross profit is what’s left of your revenue once the direct cost of delivering a service has been subtracted. It’s the number most agency founders assume they understand right up until they’re asked to calculate it for a specific client. The confusion comes when you try to decide what actually counts as a direct cost in a business that sells time and expertise rather than physical goods, and that’s where most generic explanations of gross profit fall short for a service business. This article works through what gross profit and cost of sales actually mean for an agency, where the common calculation mistakes happen, and why the benchmark figures you’ll find elsewhere online are less useful than they look.

What gross profit actually means

The gross profit formula

Gross profit is revenue minus cost of sales, sometimes called cost of goods sold or COGS. The result tells you how much money is left from each pound of revenue before any of the business’s overhead, such as rent, software, or admin salaries, has been paid. Expressed as a percentage of revenue, this becomes gross margin, and it’s the figure most commonly used to compare performance between periods, between clients, or against the rest of the business.

What gross profit isn’t

It’s worth being precise about what gross profit is not. It isn’t the same as net profit, which comes after every other cost in the business has been deducted, and it isn’t the same as EBITDA, which strips out costs like depreciation and interest to show a normalised view of earnings. All three numbers matter, but they answer different questions. Conflating them is one of the more common reasons founders misjudge how healthy their business actually is. A business can be entirely healthy on one of these measures and quietly struggling on another, which is exactly why gross profit deserves to be looked at on its own terms rather than folded into a general sense of “profitability.” We’ll come back to the distinction between all three in more detail later in this piece.

Why gross profit matters first

Gross profit also tends to be the first number a fractional CFO looks at when getting to know a new client, precisely because it’s close to the operational reality of the business. Net profit can be affected by one-off costs, tax timing, or how the founder chooses to extract money from the business. Gross profit, calculated consistently, is a much cleaner read on whether the core service delivery is fundamentally profitable before any of those other factors are layered on top.

What counts as cost of sales in a service business

Most explanations of cost of sales are written with a product business in mind, raw materials, manufacturing, packaging, and are largely useless to an agency trying to work out its own numbers. In a service business, cost of sales is built from a different set of ingredients entirely.

What belongs in cost of sales

The largest component is usually staff time spent directly delivering client work. This includes salary, employer’s National Insurance, and pension contributions for anyone whose time is billed or billable against a specific client, whether that’s a designer, a strategist, or an account handler doing hands-on delivery rather than pure client management. Freelancer and subcontractor costs sit here too, along with any production spend, media buying, or third-party tools bought specifically to deliver a piece of client work.

What doesn’t belong in cost of sales

What doesn’t belong in cost of sales is anything that keeps the business running regardless of whether a particular project exists. Rent, general software subscriptions, marketing the agency’s own services, and the founder’s own salary where it isn’t tied to delivering chargeable work, these are overheads, and they sit below the gross profit line, not above it. The distinction matters because misclassifying overhead as cost of sales, or the reverse, inflates or deflates gross margin in a way that quietly distorts every decision built on top of it, from pricing to hiring to whether a client relationship is actually worth keeping.

Staff time that sits in between

Where this gets genuinely difficult is time that sits in between. A senior strategist who spends half their week on chargeable delivery and half on running the agency isn’t a clean fit for either category, and how that split gets treated has a real effect on the margin figure a founder ends up looking at. The same problem shows up with account managers, whose time is often part client-facing delivery and part internal administration, and with founders themselves, who frequently do a mix of both without any system for separating the two. A production lead who spends most of a week on one client’s campaign but also handles internal process improvements for an afternoon is a smaller-scale version of the same issue, and multiplied across a whole team, these small misclassifications add up to a gross margin figure that doesn’t reflect reality particularly closely. A reasonable approach is to track time honestly, even approximately, and apportion cost accordingly, rather than defaulting to putting all of a senior person’s cost into overhead simply because their role is hard to categorise cleanly.

Why the gross margin range you’ll find online doesn’t tell you much

The 50-70% range everyone quotes

Search for ‘healthy gross margin for a UK agency’ and you’ll find a fairly consistent answer: somewhere between 50% and 70%. It’s quoted often enough, and confidently enough, that it’s easy to treat as settled fact, the kind of number worth measuring yourself against without asking too many questions about where it came from.

Why the range doesn’t hold up

It isn’t settled, and it’s worth being direct about why. That range moves by more than 20 percentage points depending on which source is quoted, and almost none of the content repeating it is built from verifiable, UK-specific, sector-wide data. Much of it is advisory framing, a target range presented as if it were an observed average.

Different sources define cost of sales differently in the first place, which means the ranges aren’t even measuring the same thing before you start comparing them. A media-buying agency that passes client ad spend through its own books will show a very different gross margin to a design studio, purely because of how revenue gets recorded, not because one business is run better than the other. A retainer-based content agency and a project-based development shop will show different patterns too, since the two pricing models carry different risk if delivery overruns.

Different agencies work differently

None of this means gross margin isn’t worth tracking, or that benchmarks are worthless in principle. It means a generic external range is close to useless as a benchmark for any specific agency, because it can’t account for YOUR service mix, your pricing model, your delivery structure, or how you’ve chosen to classify the time that sits between chargeable and non-chargeable work. Two genuinely well-run agencies in the same subsector can carry different healthy margins for entirely legitimate reasons, and neither number tells you much about the other.

What ACC sees in practice

One example from our own client work makes this concrete. Over the last 12 months, gross margin for one agency client has averaged around 58%, but has moved between roughly 40% and 70% depending on the period, a wider swing than any published range would suggest is normal.

In the first half of 2026 alone, the margin climbed from 49% in January to 69% in June, averaging 63% across the six months. What’s notable is where that improvement came from. It wasn’t cost-cutting. Revenue scaled materially while cost of sales stayed comparatively controlled, and by June, revenue was running around 21% ahead of budget while cost of sales sat roughly 14% below it. The extra revenue converted into gross profit far more efficiently than the business had budgeted for.

One size does not fit all

There’s a clear mechanism behind this, not just a lucky quarter. Once monthly revenue moved consistently above the £100,000 mark, more of the existing delivery cost base was being absorbed by that revenue, and margin expanded as a result, a genuine operating leverage effect rather than anything to do with pricing changes. There’s still margin upside sitting on the table too, this particular business continues to work on utilisation and non-billable time among employed delivery staff, exactly the kind of leakage covered earlier in this piece. The honest conclusion isn’t that 58%, or 63%, or 69% is the number to aim for. It’s that gross margin moves with revenue scale, utilisation, delivery mix, and how efficiently the existing cost base is being used, which is precisely why a single external benchmark can’t tell you much about where your own agency stands.

Track your own gross profit instead

The number worth tracking isn’t a published range. It’s your own gross margin, calculated consistently, broken down by client rather than blended into a single company-wide figure, and reviewed monthly rather than once a year. That’s the only version of this number that reflects your business rather than an average of businesses that may look nothing like yours, and it’s the number a fractional CFO will build your reporting around rather than a benchmark pulled from a search result.

Cost of sales formula and a worked example

The gross profit margin formula

The formula itself is straightforward. Gross profit equals revenue minus cost of sales. Expressed as a percentage, gross margin equals gross profit divided by revenue, multiplied by 100.

A worked example

Take an agency running a £10,000 monthly retainer. If the direct cost of delivering that retainer, the account team’s time, a freelancer brought in for overflow capacity, and a couple of paid tools used specifically on that account, comes to £4,500, gross profit on that retainer is £5,500. Gross margin is £5,500 divided by £10,000, which comes to 55%.

Calculate this client by client

The same calculation applied client by client, rather than only at the whole-business level, is where it becomes genuinely useful. Two clients billing the same £10,000 a month can carry very different delivery costs depending on how much senior time they need, how efficiently the work has been scoped, and how much has quietly crept beyond what was originally priced. A blended, agency-wide gross margin can look perfectly healthy while hiding one or two clients that are barely breaking even, and without a client-level breakdown, that’s invisible in the headline number.

Monthly figures are crucial

Running this calculation monthly rather than annually also matters more than it might seem. A client relationship that starts at a healthy 55% margin can drift down over several months as scope quietly expands without a corresponding increase in price, and a monthly view catches that drift while there’s still time to address it, rather than discovering it retrospectively at year end.

A note on VAT

One technical point worth getting right from the start: revenue and cost of sales figures used in this calculation should both be VAT-exclusive. It’s an easy mistake to make when pulling numbers straight from invoices, since VAT-inclusive figures are what most people are used to looking at day to day. However, including VAT on one side of the calculation and not the other, or on both when it shouldn’t be there at all, distorts the resulting margin without it being obvious that anything has gone wrong.

Common gross profit calculation errors

Inconsistent classification month to month

The most frequent mistake is treating cost of sales inconsistently from month to month. If a freelancer invoice gets classified as overhead in one month and cost of sales in the next, the resulting gross margin trend is meaningless, even though each individual number might be technically correct in isolation.

Blended margin hiding client-level problems

The second is calculating gross margin only at the whole-agency level. A healthy blended figure of 55% might be built from one client at 70% and another at 15%, and only the client-level view shows you which one needs attention, whether that means repricing, rescoping, or having an honest conversation about whether the relationship is worth keeping.

Excluding the founder’s own delivery time

The third is excluding the founder’s own delivery time when they are genuinely doing chargeable client work. If a founder bills fifteen hours a week to client delivery but takes no notional cost for that time through cost of sales, gross margin looks artificially strong, right up until that founder tries to step back from delivery and discovers the true cost of replacing their own time with someone paid a market rate.

Cost assumptions that haven’t kept up with the business

A fourth, quieter error is failing to revisit cost of sales assumptions as the business changes. A cost structure built when the agency had three staff and no freelancers doesn’t necessarily still hold once the team has doubled and a chunk of delivery has shifted to subcontractors, and gross margin calculated on outdated assumptions can be confidently wrong for months before anyone notices.

Gross margin, net margin, and EBITDA: how they differ

These three figures are often used loosely and interchangeably, and that’s a genuine problem, because they answer different questions and a business can look healthy on one while masking a real issue on another.

Gross margin

Gross margin measures delivery efficiency: how much is left once the direct cost of the work has been covered. It’s the number most directly within a team’s control day to day, since it responds to scoping, pricing, and delivery efficiency rather than to broader business decisions.

Net margin

Net margin measures what’s actually left once every cost in the business, overhead included, has been paid, and it’s almost always a smaller number than founders expect, since it absorbs everything gross margin doesn’t: rent, software, marketing the agency’s own services, admin salaries, and everything else that keeps the lights on regardless of how any single project performs.

EBITDA

EBITDA sits between the two conceptually, and slightly apart from both in what it’s used for. It adjusts net profit by adding back interest, tax, depreciation, and amortisation, which makes it useful for comparing underlying performance between businesses with different financing or asset structures, something that matters most clearly when a business is being valued or sold. For more on how EBITDA is calculated, what gets added back, and why buyers scrutinise it so closely during due diligence, see our guide to EBITDA for agency founders.

Why the difference matters

A business can have a strong gross margin and a weak net margin if overheads have crept up unchecked, growing faster than the revenue meant to support them. It can also have a healthy net margin that looks better than it is because gross margin has been miscalculated in the first place, with costs that belong in cost of sales sitting in overhead instead and flattering both figures at once. Knowing which number you’re looking at, and what it can and can’t tell you, matters more than any single figure in isolation.

How gross margin should inform pricing

Gross margin isn’t just a reporting metric produced after the fact. It’s one of the more direct inputs into whether a piece of work is actually worth taking on in the first place. A retainer priced without a clear view of its likely delivery cost is a guess dressed up as a quote, and the agencies that price most confidently are usually the ones that know their cost of sales client by client, not just in aggregate at the end of the year.

Pricing models carry different margin risk

This connects directly to a pricing decision most agencies make without quite realising they’re making it: whether to price by the hour, by a fixed retainer, or by value delivered. Each of these models has a different relationship to gross margin, since each one changes how exposed the agency is when delivery takes longer than expected. Hourly pricing protects margin but creates friction with clients who scrutinise every line. Fixed retainers protect the client relationship but leave the agency absorbing the cost if scope creeps beyond what was priced. Value-based pricing can produce the strongest margins of the three, but only where the agency has enough confidence in its own delivery cost to price ahead of the work rather than in response to it. Our article on pricing strategy and contribution margin goes into this in more depth, but the starting point is the same number this article has been building toward: know your gross margin at the client level before you decide what to charge, not after the work is already underway.

Tracking gross margin in management accounts

Why annual figures aren’t enough

None of this works as a one-off exercise. Gross margin calculated once a year, at the same time as statutory accounts, tells a founder what happened, not what’s happening now, by which point the business has often moved past whatever the number would have flagged, for better or worse.

Building this into monthly reporting

This is exactly the gap that monthly management accounts are built to close. Revenue and cost of sales broken down by client, reviewed monthly rather than annually, turns gross margin from a historical fact into something a founder can actually act on, before a thin-margin client renews on the same terms, or before a well-priced client quietly becomes unprofitable through scope creep nobody tracked at the time.

The discipline that makes this work isn’t complicated. It’s consistency: the same cost categorisation applied the same way every month, reviewed at the client level rather than only at the top line, so that a shift in margin shows up as a signal worth investigating rather than disappearing into an annual average.

A practical first step

For a founder starting from nothing more sophisticated than an annual set of accounts, the practical first step is smaller than it sounds. Pick one month, classify every cost against it as either cost of sales or overhead using the distinctions set out earlier in this piece, and calculate gross margin for the business as a whole and for your two or three largest clients. That single exercise, repeated consistently from then on, does more to build genuine financial visibility than any benchmark ever will.

Gross profit and cost of sales are foundational numbers, and getting them right matters more than most founders assume when they first start tracking them. But they only earn their keep when they’re calculated consistently and broken down at the level where decisions actually get made, client by client, month by month, rather than checked once a year as a single blended figure. A generic benchmark, whatever range it quotes, will always tell you less about your business than your own numbers, tracked properly, ever will.

Getting the right support in your agency

This article is intended for general information and does not constitute legal, tax, or financial advice. Every business is different, and founders should take appropriate professional advice based on their specific circumstances.

Frequently Asked Questions

What is gross profit?

Gross profit is revenue minus the direct cost of delivering a product or service, known as cost of sales or cost of goods sold. It shows how much money is left before the business’s overheads, such as rent and admin salaries, have been paid, and is usually expressed as a percentage of revenue called gross margin.

How do you calculate cost of sales for a service business?

Cost of sales for a service business includes staff time spent directly delivering client work, freelancer and subcontractor costs, and any production spend or tools bought specifically for a piece of client work. It excludes overheads like rent, general software, and non-billable salaries, which sit below the gross profit line.

What’s a good gross margin for a UK agency?

Most published ranges quote somewhere between 50% and 70%, but this figure varies by more than 20 percentage points depending on the source, and very little of it is verifiable, UK-specific data. A generic benchmark can’t account for your service mix or pricing model, so the more useful number is your own gross margin, tracked consistently and broken down by client.

What’s the difference between gross profit and EBITDA?

Gross profit measures what’s left after the direct cost of delivering the work, before overheads are deducted. EBITDA measures earnings after all operating costs but before interest, tax, depreciation, and amortisation, and is used most often when comparing underlying performance between businesses or preparing for a sale.

Glossary of Terms

Blended margin

A single gross margin figure calculated across the whole agency rather than broken down by client, which can look healthy while masking one or two clients running close to unprofitable.

COGS (Cost of Goods Sold)

The standard accounting term for cost of sales, more commonly associated with product businesses but interchangeable with cost of sales in a service context.

EBITDA

Earnings before interest, tax, depreciation and amortisation. An adjusted version of profit used to compare underlying performance between businesses with different financing or asset structures, most relevant when a business is being valued or sold.

Gross margin

Gross profit expressed as a percentage of revenue, used to compare performance between periods, clients, or against the wider business.

Net margin

What remains of revenue once every cost in the business, overhead included, has been deducted, expressed as a percentage. Almost always smaller than founders expect.

Overhead

Costs that keep the business running regardless of any specific client or project, such as rent, general software subscriptions, and salaries not tied to chargeable delivery.