ACOS vs ROAS vs TACOS: What Each One Measures

Three acronyms, two actual ideas. ACOS and ROAS describe the same relationship from opposite ends. TACOS asks a genuinely different question — what your advertising costs against everything you sell, not just what the ads sold.

The three formulas

Written out side by side, the differences are easy to see:

ACOS and ROAS are the same number

They are reciprocals. Convert between them with ROAS = 100 ÷ ACOS, or ACOS = 100 ÷ ROAS.

Neither is more accurate; the preference is cultural. Amazon sellers and KDP authors generally talk in ACOS because it sits naturally beside a royalty percentage. Agencies and e-commerce teams tend to use ROAS because it reads like a return.

TACOS is the one that tells you something new

TACOS — Total Advertising Cost of Sale — divides your ad spend by all your sales, advertised or not:

If you spent $200 on ads, those ads produced $500, and you sold $2,000 in total, your ACOS is 40% but your TACOS is 10%. The ads accounted for a quarter of your revenue and a tenth of your total cost base.

The gap between the two is the interesting part. A falling TACOS while ACOS stays flat is the clearest sign advertising is doing its real job — buying rank and visibility that then produce organic sales you did not pay for.

Which one to use

They answer different questions, so the honest answer is that you need more than one:

• Judging a keyword or a campaign? ACOS. It is per-campaign, per-keyword, and comparable across sizes.
• Reporting to someone who thinks in returns? ROAS. Same fact, friendlier shape.
• Deciding whether advertising is building the business? TACOS, tracked over months. A single month tells you almost nothing; a trend tells you a great deal.
• Deciding whether to keep a book advertised at all? Break-even ACOS against your actual royalty — not a benchmark from someone else's catalogue.

A worked month

One book, one month: $300 of ad spend, $750 of ad-attributed sales, $2,500 of total sales.

Same month, three true statements. The 40% looks marginal; the 12% suggests the advertising is a modest share of a business that is mostly selling on its own — which is usually a healthy place to be.

Common questions

What is the difference between ACOS and TACOS?

ACOS divides ad spend by the sales the ads produced. TACOS divides the same ad spend by your total sales, advertised and organic. ACOS judges the advertising; TACOS judges advertising's weight in the whole business.

How do I convert ACOS to ROAS?

Divide 100 by the ACOS percentage. 25% ACOS is 4.0 ROAS. The same arithmetic works in reverse: 100 ÷ ROAS gives ACOS.

What is a good TACOS?

It depends on what you are trying to do. A book being actively launched may sit at 25–40% while you buy visibility. An established title ticking over often sits in single figures. What matters far more than the level is the direction over several months.

Is TACOS better than ACOS?

Neither replaces the other. TACOS cannot tell you which keyword to cut, and ACOS cannot tell you whether advertising is growing your organic sales. Use ACOS for decisions inside a campaign and TACOS for decisions about the book.

What is the TACOS formula?

TACOS = (total ad spend ÷ total sales) × 100, where total sales includes both advertised and organic revenue for the same period.