MEET TODAY’S GUEST
Eren Atli, Founder, Secret Calculator
Rounds.com, the AI platform for mobile assets, acquired Secret Calculator, a photo vault app hidden inside a calculator, and the sale became fuel for its founder's other apps.
Eren Atli is the founder of Secret Calculator. He told his story on camera for Rounds Insights, and the full interview is below.
In short: Eren Atli built Secret Calculator, a working calculator that hides a private photo vault behind a secret equation. It grew in India, then the United States, then Japan, and a switch to hybrid monetization let him earn from non-paying users too. He sold the app to Rounds.com, the AI platform for mobile assets, and used the capital to grow his other apps.
WATCH THE INTERVIEW
Hey there!
I'm Brian Jay. If you love the app you built and still wonder whether selling it could help you grow, Eren's story is a good place to start. Let's dive in.
THE CASE STUDY
A Calculator With a Secret
Why a photo vault had to look like something else.
The idea. Eren and his brother used to take work photos for audits and control checks, and those photos had to stay private. A normal hidden gallery still tells people there is something to hide.
The product. Secret Calculator works like any calculator. Enter the equation you chose, and it opens your private gallery.
The hard part. For a photo app, the hardest work was keeping photos safe, secure, anonymized and out of reach of third parties.
Growth by Trying, Then a Hybrid Model
A/B tests, new markets and ads that don't spoil the experience.
The markets. The team tried several markets. Some worked, some didn't. They even tried Japan, where they barely knew the language. Constant A/B tests, new content and different CTAs showed what worked. The app grew in India, then the United States, then Japan.
The monetization. Daily active users were high, but few subscribed. So they moved from subscription to hybrid monetization, with banner and interstitial ads placed so they don't hurt the experience, "just like the Spotify model."
This actually helped us to grow monetization because we could have also monetized the non-paying users.
— Eren Atli
The signal. Eren knew the app was worth something when people started finding it on their own. "People were just finding this app and using it, and then we weren't actually doing anything to acquire them."
Selling One App to Grow the Others
The breaking point, the trust question and what came next.
The decision. It was hard, because he really liked the app and the idea. The breaking point was the capital: selling one app could fund all his other apps.
Selling this app to Rounds actually really fueled our growth in our different apps.
— Eren Atli
The trust. He didn't know the company, but he knew escrow from earlier deals. Then he met a founder who had sold an app to Rounds.com six months before, and read good things on Reddit. "Our code due diligence went really well," and the team was "really helpful, easy to reach."
The result. Downloads and revenue rose across his other apps, with bigger marketing budgets and new markets. His spending even reached the point where a mobile measurement partner (MMP) made sense.
3 Rules From Eren's Exit
▶ Find a Working Equation: "You spend one dollar on an app, then you earn two dollars from the customers, then double it down."
▶ Monetize Everyone, Gently: Ads that respect the experience can earn from users who never subscribe.
▶ Use a Sale as Fuel: When the time is right, sell and put the capital into your next apps, markets and experiments.
FAQ
Who is Eren Atli?
Eren Atli is the founder of Secret Calculator, a photo vault app he sold to Rounds.com, the AI platform for mobile assets.
What is Secret Calculator?
A working calculator that opens a private photo gallery when you enter a secret equation.
How did Secret Calculator make more money?
By moving from subscription only to hybrid monetization, with banner and interstitial ads placed so they don't hurt the experience.
When did Eren know the app was worth selling?
When people started downloading it organically, without any ads bringing them in.
What did the sale change?
The capital funded growth in his other apps: higher downloads, higher revenue and bigger marketing budgets.
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