The cost-revenue ratio (CRR) is the share of revenue spent on the marketing that produced it: advertising cost divided by revenue, expressed as a percentage. A shop that spends 2,000 euros on search ads and books 10,000 euros of sales from them has a cost-revenue ratio of 20%. In German-speaking markets the same figure is called the Kosten-Umsatz-Relation, abbreviated KUR, and sometimes Kosten-Umsatz-Verhältnis (KUV). It exists because retailers and their agencies wanted an efficiency number that reads like a cost line in a budget - a percentage of turnover that can be set against gross margin - rather than a multiple of spend. Lower is better.

The arithmetic

The core formula is consistent across sources. Yandex, which uses the term in its Direct ad platform and Metrica analytics product, defines CRR in its glossary as "the ratio of total ad expenses to the revenue generated, expressed as a percentage." Adspert, a Berlin-based bid management tool, gives it as advertising costs divided by shopping basket revenue, and states that the Amazon equivalent is ACoS.

Because the numerator and denominator are the same two numbers used in return on ad spend (ROAS), only flipped, the two metrics convert directly. Cost-revenue ratio = 1 / ROAS. A ROAS of 4 is a KUR of 25%. A ROAS of 5 is 20%, and a ROAS of 10 is 10%. Smarter Ecommerce (smec), the Linz-based Shopping bid management company, put it plainly in a November 2015 blog post by Thomas Otzasek: "The CRR is the inverse ROAS," adding that "to optimize CRR means to minimize it."

The useful property of the percentage form is that it sits next to margin. A retailer with a 30% gross margin after cost of goods breaks even on an order when the cost-revenue ratio reaches 30%. At a KUR of 20%, ten points of margin remain to cover fulfilment, payment fees and overheads. At 35%, every attributed sale loses money before any overhead is counted. The same thresholds expressed as ROAS targets (3.33 and 5) are identical arithmetic, but harder to read off a profit and loss statement.

What goes in the numerator and denominator

The formula is settled. The inputs are not.

Media cost only. Yandex and Adspert count advertising spend alone. Yandex Metrica's metric is described as the "share of advertising spending in the total revenue passed to Yandex.Metrica as ecommerce data."

Media plus agency fee. Rheinwunder, a German online marketing agency, includes the agency's fee in its definition, last updated on 7 October 2026 by Ralph Grundmann, and distinguishes the result from cost per order (CPO), which uses media budget alone. Its worked example: 100 ads at 1.50 euros per click and 100 clicks each cost 15,000 euros; at a 5% conversion rate and a 50-euro basket they produce 25,000 euros in revenue, a KUR of 60%. Adding 2,000 euros of agency cost lifts it to 68%, which the agency calls "far too high" for search advertising.

All marketing cost. Wolf of SEO, a German SEO consultancy, extends the numerator to indirect costs including marketing salaries, content production, market research and CRM software.

The denominator varies just as much. Revenue can mean gross basket value including VAT (19% at the standard German rate), net revenue excluding VAT, or revenue after returns and cancellations. In Germany the returns question is large. The University of Bamberg's Forschungsgruppe Retourenmanagement estimated that nearly one in four parcels ordered online in Germany in 2021 was sent back - about 530 million return shipments containing 1.3 billion items - and that 88.7% of German retailers offered free returns, against 52.4% elsewhere in the EU. A fashion retailer measuring KUR on gross basket value before returns can report a figure several points better than its finance department would recognise.

Where it sits in the buying workflow

Few ad platforms expose the ratio as a native setting. Google Ads and Microsoft Advertising bid toward target ROAS, which Google's help centre defines as "the average conversion value (for example, revenue) you'd like to get for each dollar you spend on ads." A German agency working to a client's target KUR of 20% therefore enters a target ROAS of 500% in the interface. For Shopping, Google requires 15 conversions per Merchant Center ID in 30 days first.

Yandex is the main exception. Its Direct platform offers a "Target cost revenue ratio" strategy, described on its advertiser news page as an updated version of the older "Optimize ROI" strategy with simpler settings; the page carries no date. Advertisers set a CRR percentage - the examples given are 10% for items sold and 15% for leads - and the system tries to generate conversions without exceeding it. Metrica reports the ratio through API metrics named ym:ev:expense<currency>EcommerceCRR and ym:ev:goal<goal_id>expense<currency>CRR, with data available from 1 February 2020.

Third-party tools sit between the two conventions. Adspert's goal-type guide, published on 13 February 2026 by Anja Mrak, lists "ACoS / CRR" as a goal alongside ROAS. Revenue-based goals unlock after 30 conversions in 30 days, and the guide warns that "any change bigger than 20% at a time might harm your performance." Its example moves a target from 20% to 16%, then to 12.8%.

Origin and evolution

The ratio itself is ordinary management accounting, and no source located for this article credits a person or company with bringing the term "Kosten-Umsatz-Relation" into online marketing. Smec's 2015 Shopping post already treats CRR as an established alternative to ROAS. German agency glossaries tie it most closely to affiliate marketing, where publishers are paid a percentage of order value: Löwenstark, a Braunschweig agency, describes KUR in a glossary entry dated 4 July 2022 as "especially relevant" for affiliate and publisher networks. A network paying 8% commission runs at a KUR of roughly 8% plus fees, which made the ratio a natural unit for comparing affiliate with paid search. PPC Land's affiliate explainer describes cost per sale, a percentage of order value, as the dominant affiliate payment model.

Amazon's advertising cost of sales (ACoS) spread the same formula to marketplace sellers under an English name. Its derivative, TACoS, divides ad spend by total rather than attributed sales.

Why it matters

For marketers in Germany, Austria and Switzerland, KUR is often the number in the contract. Agencies are briefed with a ceiling, and the conversion to ROAS happens inside the account. The German online market is large enough for that translation to matter: the Handelsverband Deutschland (HDE) said in its Online-Monitor on 3 June 2026 that marketplaces handled 56.7% of German online sales in 2025 and forecast nominal online growth of 4.3% for 2026.

The ratio's sensitivity to the platform's own value figures has become a live issue. Google lets advertisers inflate conversion values for bidding: in October 2026 it moved percentage multipliers of 1.1x to 5x for new customers out of beta. A 100-euro purchase valued at 120 euros produces a better reported KUR than the cash ledger shows. Google added an Original conversion value column in November 2025 so advertisers could see values before such rules were applied.

Limitations and disputes

It is not profit. A 20% KUR is excellent on a product with a 60% margin and ruinous on one with 15%.

It is an average. The ratio describes all spend together and says nothing about the last euro.

It inherits attribution. The revenue in the denominator is what the platform or analytics tool credits to ads, under its own lookback windows and models. Whether those sales would have happened anyway is the question addressed by incrementality testing, which the ratio cannot answer.

It lacks a standard. As the sources above show, two agencies can report different KURs for the same account depending on whether they include fees, VAT and returns. Benchmarks are therefore hard to compare. Rheinwunder calls 15% to 25% sustainable for a shop with a 50% overall margin, while Wolf of SEO declines to give any figure, arguing benchmarks vary by industry.

Not the same as

ACoS. Identical formula, but specific to Amazon Ads and its attributed sales. ACoS is a cost-revenue ratio; a cost-revenue ratio need not be ACoS.

Cost-to-income ratio. A banking efficiency measure dividing operating costs by operating income. The European Central Bank reported an aggregate 53.06% for significant euro area institutions in the second quarter of 2026, down from 54.20% a year earlier. It has nothing to do with advertising.

Cost of revenue. An accounting line in company financial statements covering the direct costs of delivering goods or services, closer to cost of goods sold than to marketing spend.

KUV as Kurs-Umsatz-Verhältnis. In German finance, KUV more commonly denotes the price-to-sales ratio of a share, an equity valuation multiple.

Recent developments

Google's 2026 bidding changes have made revenue targets behave more like instructions. On 16 June 2026 Google said Target CPA and Target ROAS would return as standalone bidding strategies in the interface, a label change that left bidding behaviour untouched; Microsoft had removed its standalone versions on 4 August 2025. A separate change effective 17 August 2026 pushed budget-limited Target CPA and Target ROAS campaigns toward their targets even when they were beating them, one of the shifts in a year when Google optimises its own revenue.

The effect on cost-revenue ratios was measurable. Smec data covered by PPC Land on 22 October 2026 showed that budget-limited campaigns lost a median 20% ROAS surplus within three weeks. Translated, a shop with a KUR ceiling of 20% that had been running at roughly 16.7% drifted back to 20% - the ceiling became the operating point.

On Amazon, an Ad Lab video published on 15 October 2026 listed ACoS and ROAS as two of four bidding metrics, though they measure one relationship.

Timeline

  • November 23, 2015 - Smarter Ecommerce blog post defines CRR as the inverse of ROAS for Google Shopping bidding.
  • February 1, 2020 - Earliest date for Yandex Metrica's cost revenue ratio metrics.
  • 2021 - University of Bamberg data: nearly one in four German online parcels returned, about 530 million return shipments.
  • July 4, 2022 - Löwenstark glossary ties KUR to affiliate and publisher network management.
  • August 4, 2025 - Microsoft Advertising removes standalone Target CPA and Target ROAS strategies.
  • October 15, 2025 - Adspert support article equates CRR with Amazon's ACoS.
  • November 2025 - Google Ads adds Original conversion value column showing values before value rules.
  • February 13, 2026 - Adspert publishes goal-type guide listing ACoS/CRR targets and a 20% step limit.
  • June 3, 2026 - HDE Online-Monitor puts marketplaces at 56.7% of German online sales in 2025.
  • June 16, 2026 - Google announces Target CPA and Target ROAS return as standalone strategy labels.
  • August 17, 2026 - Google's budget-limited bidding change takes effect.
  • October 7, 2026 - Rheinwunder updates its KUR definition, including agency fees in the numerator.
  • October 22, 2026 - Google moves new-customer value multipliers of 1.1x to 5x out of beta; smec data shows the ROAS surplus on budget-limited campaigns gone by August 31.

Summary

  • Who: Online retailers, performance agencies and affiliate managers, particularly in Germany, Austria and Switzerland, set and report the ratio; Yandex uses it natively in Direct and Metrica; bid tools such as Adspert and smec support it; Amazon reports the same formula as ACoS.
  • What: Advertising (or marketing) cost divided by the revenue it generated, as a percentage. It is the inverse of ROAS, so a KUR of 20% equals a ROAS of 5, and it is read against gross margin to judge profitability.
  • When: A long-standing retail accounting ratio, documented in online marketing at least since 2015; Yandex Metrica data runs from February 2020, and Google's August 17, 2026 bidding change made revenue targets more binding.
  • Where: Google Ads and Microsoft Advertising accounts (entered as target ROAS), Yandex Direct (entered directly), Amazon Ads (as ACoS), affiliate networks and agency reporting across the DACH region.
  • Why: It expresses ad efficiency as a share of turnover that can be compared with margin, though its value depends on platform attribution, conversion value rules and whether fees, VAT and returns are counted.