What it means
The metric started in online advertising, where large platforms pay partners to send them search or display traffic and disclose that payment as a separate line. It has since been adopted by any business that buys visitors rather than earning them, which today means most consumer companies.
TAC differs from customer acquisition cost in what it counts. TAC measures the cost of getting a visitor to arrive, while customer acquisition cost measures the cost of turning strangers into paying customers, so TAC divided by the conversion rate roughly gets you from one to the other.
Reported as a percentage of revenue, TAC is a quick read on how much of each sales dollar is being handed straight back to advertising platforms and partners. A business at 15% keeps 85 cents of every dollar to cover product, delivery and overheads; one at 45% is running on borrowed time unless its margins are unusually fat.
The number tends to worsen quietly as a company scales. The cheapest, most intent-driven traffic gets bought first, and each additional increment of volume comes from broader audiences that convert less well, so TAC as a percentage of revenue drifts upwards even when the marketing team does nothing wrong.
The most important nuance is attribution. Where a business also gets meaningful organic or direct traffic, dividing total paid spend by total revenue understates the real cost of paid visitors, so serious operators calculate TAC against the revenue that paid channels actually produced.
In practice
Real-world examples.
Example
A price comparison website pays affiliates a commission on every click sent to insurers. Those commissions are its single largest cost line at 38% of revenue, so a one-point move in the rate changes group profit by hundreds of thousands of dollars.
Example
A subscription meal box brand runs TAC at 22% of first-order revenue but only 6% when measured across the customer's first twelve months. Management reports both figures because the first drives cash planning and the second drives investment decisions.
Example
A regional car dealership group spends $180,000 a quarter on paid search that delivers 90,000 visits, a TAC per visitor of $2.00. Because a single sale generates several thousand dollars of gross profit, that cost is easily justified even at a low conversion rate.
Formula
Calculation
TAC as % of Revenue = Traffic Acquisition Spend / Revenue from That Traffic
TAC per Visitor = Traffic Acquisition Spend / Visitors Acquired
An online homeware retailer spends $1,350,000 in a year on paid search, paid social and affiliate commissions. That spend delivers 2,700,000 visits, which generate $4,500,000 of attributed revenue.
Step 1: TAC as % of revenue = $1,350,000 / $4,500,000 = 0.30, or 30%
Step 2: TAC per visitor = $1,350,000 / 2,700,000 = $0.50
Step 3: Revenue per visitor = $4,500,000 / 2,700,000 = $1.67
Every visitor costs 50 cents to acquire and produces $1.67 of revenue, leaving $1.17 per visitor to cover cost of goods, fulfilment and overheads. If the gross margin on those goods is 45%, the visitor contributes about $0.75 of gross profit against $0.50 of acquisition cost, which is a thin but workable 1.5 times return.Case study
Seen in the real world.
The following is an illustrative and entirely fictional case. Quillon Home, an invented online homeware retailer, hit $4,500,000 of revenue in its third year and celebrated growing faster than plan. Its board only asked about traffic acquisition cost when the cash forecast turned negative.
The finance team found paid spend of $1,350,000 against that revenue, a TAC of 30%, up from 19% two years earlier. Digging into channels showed the deterioration was concentrated in broad-match search terms added to chase volume, which were converting at less than a third of the rate of the brand terms.
Quillon capped spend on the worst-performing terms, shifted budget into email and referral programmes that carried no per-visit cost, and set a standing rule that TAC would not exceed 24% of attributed revenue in any quarter. Growth slowed to a fifth of the previous rate for two quarters, but the illustrative company was cash-positive by the end of the year.
Watch out
Common mistakes.
- Dividing paid spend by total revenue including organic sales. This flatters the ratio and hides how expensive the paid channel really is.
- Treating TAC and customer acquisition cost as the same thing. TAC buys a visit, while customer acquisition cost buys a customer, and the gap between them is the conversion rate.
- Judging TAC on first-order revenue only for a repeat-purchase business. A 40% TAC on the first order can be perfectly sound if customers reorder four times over two years.
Questions
People also ask.
Should TAC include agency fees and salaries?
Most definitions include the money paid to platforms and partners for traffic itself, with internal costs reported separately, but the treatment should at least be consistent period to period.
What is a healthy TAC percentage?
It depends almost entirely on gross margin, with high-margin digital products tolerating 30% to 40% while low-margin resellers usually need to stay below 10%.
Why does TAC usually rise as a business grows?
Because the most efficient traffic is bought first, and each additional increment comes from less targeted audiences that cost more per converted sale.
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