ROI (Return on Investment): Definition, Bedeutung & Beispiele im Direktmarketing

What is ROI? -- Definition, Formula, and Differentiation

ROI (Return on Investment) is the central metric for evaluating the profitability of an investment. The formula is: ROI = (Profit - Investment) / Investment x 100. The result in percentage shows how much net profit each invested dollar generates. The term originates from the DuPont ratio system, developed in 1919 by the US chemical corporation DuPont and considered the oldest ratio system in business economics.

In direct marketing, ROI is frequently confused with ROAS (Return on Ad Spend) -- but the distinction is crucial. ROAS measures revenue in relation to advertising spend: A ROAS of 1,011 percent (CMC 2025) means that each advertising dollar generates $10.11 in revenue -- not profit. ROI, on the other hand, accounts for all costs (printing, postage, lettershop, cost of goods) and measures net profit. For operational campaign management, ROAS is the more common metric; for overall profitability assessment, ROI is decisive.

A third variant is ROMI (Return on Marketing Investment), which relates total marketing return to marketing costs. In practice, all three metrics are used -- what's crucial is that comparisons between campaigns or channels always use the same metric.

ROI in Channel Comparison: Why Direct Mail Performs Above Average

Available benchmark data shows a consistent picture: Direct Mail achieves the highest ROI of all direct marketing channels. The ANA Response Rate Report 2021 determined a median ROI of 112 percent for Direct Mail -- compared to 93 percent for email, 88 percent for paid search, and 81 percent for social media. For house lists (existing customers), ROI even rises to 161 percent.

A controlled field study by MIT Sloan Management Review (Zhang, 2025) with an e-commerce company provides the most precise channel comparison under controlled conditions to date: Direct Mail achieved a ROAS of 55 percent -- compared to 21.4 percent for Google, 15 percent for Amazon, and 4.7 percent for Facebook. Customer acquisition costs (CPA) were $37.50 for Direct Mail, compared to $50 for Google and $45 for Facebook. Average order value was also higher at $75 compared to digital channels ($58-65).

In the German market, the CMC studies by Deutsche Post confirm these results on a broad data basis: The CMC Print Mailing Study 2025 examined 1,157,674 mailings from 43 online retailers and determined an average ROAS of 1,011 percent for existing customers. Cart value increased by 13 percent compared to the previous order. Particularly noteworthy: 47 percent of orders came in only after the fifth week post-mailing -- a long-term effect that no digital channel offers in this form.

ROI Calculation for Direct Mail: How to Calculate Concretely

The ROI calculation for direct mail follows a clear formula. Total costs consist of three components: postage (presorted mail from $0.38/piece for standard letters at 5,000+ items), printing and personalization ($0.12-0.25 depending on format and volume), and lettershop (enveloping, addressing). Per mailing, typical total costs range from $0.50 to $0.80.

Sample calculation for 1,000 existing customer mailings: With total costs of $0.65 per piece ($650 total) and a conversion rate of 4 percent (CMC average), 40 recipients purchase with an average cart value of $80. Revenue is $3,200, ROAS is 492 percent. With a 50 percent margin, this yields gross profit of $1,600, minus $650 campaign costs equals profit of $950 -- corresponding to a ROI of 146 percent.

The break-even point can also be calculated: At $0.65 cost per mailing and $40 profit per order ($80 cart at 50 percent margin), the campaign needs only 16.25 orders from 1,000 mailings -- a break-even response rate of 1.6 percent. Since existing customer mailings achieve 4 to 5 percent conversion according to CMC data, actual response is significantly above break-even. Even for new customer mailings averaging 1 percent response (CMC 2021), profitability can be achieved with higher cart values -- CPO was $40 with a ROAS of 250 percent.

ROI Drivers: What Determines Campaign Success

Four factors significantly determine the ROI of a print mailing campaign: format, personalization, segmentation, and timing.

For format, the CMC Dialogpost Study 2020 shows clear differences: The classic advertising letter achieves a CVR of 5.7 percent -- that's 25 percent more than maxi postcards or self-mailers (each 4.6 percent). The ROAS of the letter format is 15 percent above the postcard and 42 percent above the self-mailer. Although the letter is more expensive to produce, it achieves higher net returns.

For personalization, the RIT study by Romano and Broudy demonstrates the strongest lever: Personalization with name and full-color image increases response rate by 135 percent; the combination of name, color, and data-driven offer by up to 500 percent. The Lob State of Direct Mail Report 2025 confirms: 88 percent of marketing executives say personalized direct mail improves response rates.

Segmentation through RFM analysis (Recency, Frequency, Monetary Value) directs advertising budget where the highest ROI occurs. The CMC Dialogpost Study 2020 shows: Customers with five or more previous orders achieve a three times higher conversion rate than one-time customers. Valentins GmbH achieved a 13 percent higher uplift through ML-based customer selection compared to conventional selection.

Timing also influences ROI: The months September through November offer the highest performance due to year-end planning and Christmas preparation. Repeated campaigns with two to four touchpoints over 30 to 90 days increase ROI by 37 percent according to JICMAIL, with 2.5 times higher response rates.

Real-World Examples: Documented ROI Results

The best documented ROI results come from controlled studies and platform analyses. In the German market, Deutsche See stands out as the best case in CMC 2025: Mailings to existing customers achieved a CVR of nearly 8 percent, a ROAS of 1,902 percent, and a cart value increase of 31 percent. The key factor: Customers save the letter and consciously use it for their order.

Internationally, automated campaigns demonstrate the ROI effect: HexClad generated $3.2 million in revenue via PostPilot in four months with a 12x ROAS through automated retention postcards. Apparel brand Taylor Stitch achieved an average 10x ROI across all campaigns and 15x ROI for win-back mailings -- without discounts, just through relevant messaging at the right time. And meal kit service Marley Spoon achieved a 263 percent higher conversion rate with print win-back mailings compared to email; direct mail drove 20 percent of all reactivations.

The Lob State of Direct Mail Report 2025 summarizes the trend: 82 percent of marketing executives plan to increase their direct mail budget in 2025, and 79 percent rank direct mail as their best-performing channel. Companies with the strongest ROI use automation 32 percent more often and leverage high-quality first-party data for segmentation.