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What is ROAS? Return on Ad Spend explained for UK SME owners

ROAS stands for Return on Ad Spend. It is the ratio of revenue generated to advertising spend. A 4x ROAS means that for every £1 spent on advertising, £4 of revenue was generated. It is the most commonly reported metric in digital marketing, and it is also one of the most frequently misunderstood.

How to calculate ROAS

ROAS = Revenue generated ÷ Advertising spend

Example: You spend £2,000 on Google Ads and generate £8,000 in attributed revenue.
ROAS = £8,000 ÷ £2,000 = 4x

What is a good ROAS for UK small businesses?

A "good" ROAS depends entirely on your gross margin. ROAS measures revenue, not profit. A 4x ROAS at a 40% gross margin generates £1.60 of gross profit per £1 spent — a strong return. A 4x ROAS at a 20% gross margin generates £0.80 of gross profit per £1 spent — marketing is losing money at the gross profit level.

Gross MarginBreak-even ROAS4x ROAS = profit ROASVerdict
20%5x0.8x (loss)Loss-making
30%3.3x1.2xMarginal
40%2.5x1.6xStrong
50%2.0x2.0xExcellent

Profit ROAS — the metric that actually matters

Profit ROAS is ROAS multiplied by your gross margin percentage. It tells you the gross profit return per £1 of marketing spend. This is the number marketing decisions should be based on, not revenue ROAS.

Profit ROAS = Revenue ROAS × Gross margin %

Example: 3.8x ROAS at 45% gross margin
Profit ROAS = 3.8 × 0.45 = 1.71x
Each £1 of marketing spend returns £1.71 of gross profit.

Break-even ROAS

Break-even ROAS is the minimum ROAS needed for marketing to cover its own cost in gross profit terms. Calculate it as: 1 ÷ gross margin. At 40% gross margin, break-even ROAS is 2.5x. Any channel consistently below this is loss-making at the gross profit level and should be cut before budget increases are considered.

ROAS by channel — why blended ROAS hides problems

Most marketing setups have significant variation between channels. A blended 3x ROAS might include one channel at 6x and another at 1.5x. The blended figure looks acceptable. The channel detail reveals that one channel is excellent and one is destroying value. Cutting the 1.5x channel and reallocating to the 6x channel typically improves blended ROAS by 30-50% without increasing total spend.

Calculate your profit ROAS by channel

The LumixAI Marketing Analysis Tool calculates ROAS and profit ROAS per channel using your gross margin. Included in every subscription.

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→ Also read: Roas calculation guide