ROAS vs MER: The Difference That Changes Your Decisions

A Google Ads account can report £6 of revenue for every £1 spent while the company’s overall marketing efficiency deteriorates.

That is the practical point of ROAS vs MER: one can improve while the other falls. If a board treats them as rival versions of the same score, it can reward channel efficiency while missing a marketing system that is becoming more expensive.

Our position is simple. Use ROAS to diagnose paid-channel performance. Use MER to decide whether the entire marketing investment is commercially sustainable.

ROAS vs MER: two different questions

Return on ad spend measures the relationship between revenue and advertising expenditure:

ROAS = revenue attributed to a paid channel ÷ media spend for that channel

If Google Ads receives £80,000 and generates £400,000 in attributed revenue, its ROAS is 5.0.

Marketing efficiency ratio uses a wider denominator:

MER = revenue in the defined business scope ÷ total marketing cost in that scope

If the business generates £1.2 million in new-business revenue after spending £300,000 across media, people, agencies, events, software and creative, its acquisition MER is 4.0.

ROAS asks: How efficiently did this advertising channel turn media spend into attributed revenue?

MER asks: How much revenue did the business produce for every pound committed to marketing?

The distinction is scope. ROAS isolates a channel. MER exposes the economics surrounding it.

Some businesses calculate MER as total revenue divided only by total media spend. That convention is usable if everyone understands it, but it is too narrow for most board-level decisions. It excludes the people, production and infrastructure required to run those campaigns. We recommend labelling that calculation “media MER” and reserving acquisition MER for the full acquisition-marketing cost base.

The revenue definition also needs to be explicit. Recognised revenue, first-year contract revenue and total contract value are not interchangeable. Pipeline is not revenue. For companies without ecommerce transactions, our guide to calculating lead-generation ROAS explains how to connect commercial outcomes to the ratio without pretending every form submission has equal value.

ROAS can still be wrong because the attributed revenue is wrong. The reasons reported Google Ads ROAS can mislead deserve separate treatment. Here, the issue is different: even an accurately calculated channel ROAS does not describe total marketing efficiency.

What MER exposes that ROAS hides

A strong ROAS result can coexist with a weak commercial result for several reasons.

The cost of making the channel work

A campaign’s media spend might be £50,000. The business may also need:

• £18,000 of agency support
• £12,000 of landing-page and creative work
• £9,000 of software and data
• £30,000 of internal team cost

ROAS sees the £50,000. A full acquisition MER denominator sees £119,000.

That does not make ROAS dishonest. It makes it incomplete for decisions about total investment.

Cost moving outside the platform

A paid search campaign may become more efficient after the company invests in new positioning, stronger case studies and better landing pages. ROAS rises because more visitors convert and sales teams close more of the resulting opportunities.

The costs behind that improvement might sit in payroll, website development or content budgets. ROAS receives the benefit without carrying those costs. MER captures both sides of the change.

This is one reason impressive account screenshots deserve scrutiny. When reviewing case studies tied to commercial outcomes, check which costs sit in the denominator and whether the reported return refers to revenue, pipeline or lead value.

Revenue growing more slowly than the cost base

A company can add campaigns, markets, tools and people while maintaining channel ROAS. Yet if marketing costs grow by 40% and new-business revenue grows by 15%, efficiency has fallen.

ROAS might not reveal that decline because each campaign is still clearing its individual target. MER will.

This matters when leaders ask whether to approve another £250,000 of annual marketing expenditure. The relevant question is not whether one account still reports 5.0 ROAS. It is whether the expanded system can produce enough additional gross profit to support its larger cost base.

Revenue that marketing did not need to reacquire

Company-wide MER can look excellent when renewals and expansions are included in the numerator. A £10 million recurring-revenue business with £1 million of marketing expenditure appears to have a MER of 10.0, even if only £1.8 million of that revenue came from new customers.

That company needs two views:

• Company MER: total revenue divided by total marketing cost
• Acquisition MER: new-business revenue divided by acquisition-marketing cost

Company MER is useful for planning the overall cost structure. Acquisition MER is the sharper measure for evaluating growth expenditure.

A worked B2B ROAS vs MER example

Consider a B2B software company comparing two mature quarterly sales cohorts. It uses first-year contract revenue consistently in both periods.

Google Ads appears to have improved substantially:

Quarter A ROAS: £416,000 ÷ £80,000 = 5.2

Quarter B ROAS: £540,000 ÷ £90,000 = 6.0

A channel-level review might recommend increasing the budget. Google produced £124,000 more attributed revenue from only £10,000 more media spend.

The company-wide acquisition figures tell a less comfortable story:

Quarter A MER: £900,000 ÷ £250,000 = 3.6

Quarter B MER: £1,050,000 ÷ £350,000 = 3.0

New-business revenue increased by £150,000, but the total marketing cost required to produce it increased by £100,000.

Assume a 65% gross margin:

• Quarter A gross profit: £900,000 × 65% = £585,000
• Quarter A gross profit after marketing: £585,000 − £250,000 = £335,000
• Quarter B gross profit: £1,050,000 × 65% = £682,500
• Quarter B gross profit after marketing: £682,500 − £350,000 = £332,500

Revenue grew, Google Ads ROAS improved and contribution after marketing fell by £2,500.

MER has exposed what ROAS could not: the wider marketing system became less efficient. That does not prove Google Ads should be cut. The extra cost might include a recent hire or campaign whose revenue has not matured. It does mean the company should not scale the whole budget merely because one channel ratio improved.

When ROAS should lead and when MER should lead

ROAS is the better operating metric when the decision sits inside a paid channel. MER is the better commercial metric when the decision changes the size or shape of the whole marketing investment.

ROAS should not be viewed alone even for channel decisions. Volume, lead quality and sales capacity still matter. A campaign with 8.0 ROAS from one deal is not automatically more useful than a repeatable campaign producing 5.0 across 20 deals.

Keyword decisions also need commercial context. A disciplined B2B Google Ads keyword strategy separates high-intent demand from broad traffic before ROAS is used to allocate money between them.

The organisational split should be equally clear. A brief for specialist Google Ads management should make the channel team accountable for traffic quality and paid-media economics. Leadership remains responsible for the total cost base, revenue definition and acceptable MER.

Neither metric should be stretched beyond the decision it can support. Asking ROAS to approve a company-wide marketing budget is like judging a factory by the electricity bill of one machine.

Making MER decision-ready for B2B sales cycles

A raw monthly MER calculation is often noisy for B2B companies. Marketing expenditure happens now; revenue may close three, six or twelve months later.

Five choices make the metric more useful.

1. Set one revenue basis

Choose recognised revenue, first-year contract revenue or another finance-approved measure. Use the same basis for ROAS and MER comparisons.

Do not put £4 million of unweighted pipeline above £300,000 of marketing cost and call the result a return. Pipeline coverage can support forecasting, but it is not earned revenue.

2. Match spend to a mature revenue window

A business with a six-month sales cycle should not divide August revenue by August marketing spend and infer that August campaigns worked.

Use mature acquisition cohorts or a trailing period long enough to smooth the delay. The right window depends on the sales cycle, contract structure and reporting basis. A broader treatment of these choices sits in our guide to reliable B2B ROAS measurement.

3. Publish the denominator

A credible MER report states what marketing cost includes. A practical acquisition denominator normally covers:

• Paid media
• Agency and freelance fees
• Marketing payroll and employment costs
• Creative and website production
• Events, sponsorships and partnerships
• Marketing software, data and research

If sales salaries and commissions are included, label the result as a sales-and-marketing efficiency ratio. Quietly changing the denominator destroys the trend.

4. Set the target from unit economics

A “good” MER is not a universal number.

If the company permits marketing to consume 20% of new-business revenue, the implied target MER is:

£1 ÷ 20% = 5.0

If it can afford 25%, the target is:

£1 ÷ 25% = 4.0

Gross margin, retention, cash collection and servicing costs determine what is affordable. A 3.0 MER can be attractive for a high-margin subscription business with strong retention and unacceptable for a low-margin consultancy with heavy delivery costs.

5. Read the trend with volume

MER can rise because revenue grew or because the company stopped investing. Those are not equivalent outcomes.

Report MER beside new-business revenue, gross profit and total marketing cost. A move from 3.5 to 4.5 accompanied by shrinking revenue may represent efficient contraction rather than healthy growth.

FAQ

Is MER the same as ROAS?

No. ROAS normally compares revenue attributed to a paid channel with that channel’s media spend. MER compares revenue across a defined business scope with the wider marketing cost required to produce it. ROAS is a channel diagnostic; MER is a business-efficiency measure.

What is a good MER for a B2B company?

The target should come from the percentage of revenue the company can afford to spend on marketing. A 20% allowance implies a 5.0 MER; a 25% allowance implies 4.0. Gross margin, contract length, retention and cash flow can move the acceptable figure materially.

Can ROAS increase while MER decreases?

Yes. Channel-attributed revenue can grow faster than media spend while payroll, creative, events, technology and other marketing costs grow faster than total revenue. The worked example above shows ROAS rising from 5.2 to 6.0 while acquisition MER falls from 3.6 to 3.0.

Should pipeline be used in MER?

Not as if it were revenue. Pipeline can be reported separately as a forward indicator, but open opportunities have not yet produced a commercial return. Use a consistent finance-approved revenue measure for the final MER calculation.

How often should a B2B company review MER?

Track it monthly for visibility, but make material decisions using mature cohorts or a trailing period suited to the sales cycle. Quarterly decision-making is often more reliable than reacting to isolated monthly movements.

Summary

• ROAS measures paid-channel efficiency; MER measures wider marketing efficiency.
• Strong ROAS can hide a growing cost base and falling contribution.
• Use ROAS for campaign decisions and MER for total budget decisions.
• Define revenue, cost scope and timing before comparing either ratio.
• Set the MER target from gross margin and affordable marketing cost, not an industry benchmark.

Actualyse builds measurement and attribution setups that tie B2B ad spend to real revenue. Book a call to talk through where yours stands.