Introduction: The Difference Between "We Are Good" and "This Is What We Achieved"
Two emails, the same service.
The first: "I help e-commerce businesses improve their Google Ads campaign performance."
The second: "For a furniture e-commerce store, I reduced the cost per order from 34 to 19 euros in three months with the same budget."
The second email is more convincing not because it is better written. It is more convincing because it contains proof.
A case study is a formalized version of this proof — and it is also one of the most underrated sales tools. Most freelancers and small agencies do not have one, even though preparing it takes just an hour of work after completing a project.
1. What a Case Study Is and What It Is Not
A case study is not: A description of what you did. A list of tools used. Praise from the client. A screenshot of the finished website.
A case study is: A story about the problem the client had, what you did about it, and what measurable result it achieved.
The key word is measurable. Without a specific number, it is a reference, not a case study. A reference says, "we were satisfied." A case study says, "the number of inquiries increased from 4 to 17 per month."
2. A Structure That Works
A case study has five parts and fits on one to two pages.
Part 1: Who is the client. One to two sentences. Industry, size, region. You don’t have to name the client if they don’t want to — "a medium-sized furniture e-commerce store in the Czech Republic" is sufficient.
Part 2: What problem they had. Specific and measurable. Not "they wanted better marketing," but "the campaigns ran for three years without change, the cost per order rose to 34 euros, and the return on investment fell below profitability."
Part 3: What you did. Specific steps, not a list of tools. Three to five points. The client reading this should understand your approach.
Part 4: What the result was. Numbers before and after, with a specified time period. This is the most important part of the entire case study.
Part 5: What the client thinks about it. Two to three sentences of direct quotation. Ideally not "we were satisfied," but something specific.
3. What Numbers to Use
Not every metric is equally convincing. The closer to money, the better.
The strongest: Revenue, number of orders, number of new customers, number of inquiries, cost savings.
Medium strength: Conversion rate, cost per order, cost per inquiry, return on ad spend.
The weakest: Website traffic, post reach, number of followers, search rankings.
Why is traffic a weak metric? Because the business owner does not sell traffic. They sell a product or service. The number that matters to them is the one that can be converted into money.
If you don’t have access to business numbers: Ask the client. "How many inquiries did you receive last month compared to the period before our collaboration?" Most clients will gladly respond — and you will get a number that sells.
4. How to Present the Numbers
Always provide the baseline. "17 inquiries per month" says nothing. "From 4 to 17 inquiries per month" says everything.
Always specify the time period. "In three months" is important information. Without it, the reader does not know if it’s a quick result or work over two years.
Use both absolute and relative numbers. "From 4 to 17 inquiries, which is an increase of 325 percent." Percentages sound impressive, absolute numbers are believable. Together they work best.
Don’t exaggerate or round up. An exact number sounds more credible than a round one. "An increase of 47 percent" sounds more realistic than "an increase of 50 percent."
If the result is not dramatic, be honest about it. A case study with a 20 percent increase is still valuable. A case study with a fabricated 400 percent increase will destroy your credibility when the client asks for details.
5. How to Obtain Consent and Materials from the Client
This is the step where most case studies fail — they never happen because no one asked for them.
Timing: The best moment is right after delivering the project or during a monthly report with good results. That’s when the client is most satisfied.
How to Ask:
"The results over the last three months are very good. I would like to prepare a short case study from this — what the problem was, what we did, and what the result was. I will send everything to you for approval before use. I would need two sentences from you about how you perceive it, and consent to use the numbers. Would that be okay?"
If the client does not want to be named: Offer an anonymized version. "A medium-sized furniture e-commerce store" works almost as well as a specific name, especially if you are targeting companies from the same industry.
If the client does not want to disclose numbers: Offer relative values instead of absolute ones. Instead of "revenue increased from 40,000 to 62,000 euros," you can say "revenue increased by 55 percent."
Always get the final version approved. The client must see exactly what you will publish. This is not a formality — it protects both the relationship and you.
6. How to Use the Case Study in Outreach
A case study is not a decoration on the website. It is a sales tool, and its main use is in outreach.
In a cold email: Don’t write the entire case study. Use one sentence with a number from it.
"For a furniture e-commerce store in a similar situation, I reduced the cost per order from 34 to 19 euros in three months. I believe there is similar potential for you."
Three sentences, a specific number, a relevant industry. That is the strongest type of first sentence you can write.
In a follow-up: Here you can send a link to the entire case study. "I’m sending a specific example from your industry — it may give you a better idea."
In a meeting: Have it ready for screen sharing. One relevant case study from the client’s industry will convince more than ten from other industries.
In a proposal: Attach a case study from a similar project as an appendix. It increases the credibility of your estimates and prices.
A practical note on targeting: A case study works best when you target companies from the same industry. At DataSend.ai, you can set filters specifically for the industry where you have results and send a campaign that references it. Relevant proof plus a relevant target audience is the strongest combination in all outreach.
7. What to Do If You Don’t Have a Case Study
If you have at least one completed project: Ask the client for numbers retroactively. Even a project from six months ago can be processed.
If you have a project without measurable results: Use at least a qualitative description — what was before, what is now, what the client appreciates. It’s weaker, but better than nothing.
If you don’t have any project: Create a sample project for a real company and document the process. You can’t provide results, but you can show your approach and thinking. Clearly label it as a concept, not as a completed project.
8. How Many Case Studies Do You Need
Less than you think. Three to five good case studies will cover most situations.
Ideal distribution: One for each industry you are targeting. One for each type of service you offer. And one that shows an exceptionally good result.
It’s better to have three strong case studies with specific numbers than fifteen vague references.
Conclusion: One Hour of Work That Sells for Years
Preparing a case study takes about an hour — summarizing the problem, steps, results, and asking the client for two sentences.
The same case study will then serve you in every cold email, at every meeting, and in every proposal. It is probably the best return on an hour of work in your entire business.
The worst thing you can do is complete a successful project and not document it. In six months, you won’t remember the numbers, and the client won’t remember the details.
Want to reach out to companies in the industry where you have results? DataSend.ai — filters by industry and region, 12.5 million companies, campaigns and pipeline in one.
