This Stupidly Simple App Makes $100K/Month

Business Summary

Michael, a 20-year-old NYU student, built Go Tall, an app that predicts users’ adult height and offers habit-tracking features. He says it averages about $100,000 in monthly revenue. The idea came from a problem he remembered having as a teenager, a similar app listed for sale on Acquire.com, and TikTok comments showing that people were eager for personalized height predictions.

The case study’s central lesson is that a seemingly simple app can become a business when it addresses a personally meaningful concern, is validated through real customer behavior, and is marketed with repeatable content.

Idea Validation and Product

• Look for validated demand: Michael found a similar height-prediction app listed for roughly $20,000 on Acquire.com. Rather than buy it, he built his own.
• Combine personal experience with observed behavior: He recalled searching for height calculators as a teenager, then saw people sharing their ages and parents’ heights in TikTok comments and asking for predictions.
• Treat direct messages as a demand signal: His TikTok account received around 10–20 DMs per day from people asking him to predict their height.
• Build an iterative product: Go Tall uses CDC growth data and research studies. Its onboarding asks users for more information to refine predictions.
• Use the initial product hook to support ongoing engagement: The final prediction is behind a paywall, while free features include stretching guidance, meal scanning, and sleep tracking. Users can log additional information, and their predictions may change over time.
• Set realistic expectations: The app promotes habits that may support users’ growth potential while acknowledging that height depends heavily on genetics and that outcomes are not guaranteed.

Growth Playbook

• Test organic content before scaling paid acquisition: Michael spent about a month experimenting with content, posting 10 TikToks per day before finding a format that worked.
• Use a repeatable content format: He replied to comments with height predictions, then reproduced the format across two accounts and had his girlfriend try it.
• Measure the funnel: With one main format and distribution channel, he could estimate how views translated into downloads and use that information to decide which creators were worth paying.
• Recruit creators through direct outreach: He messaged about 50 people per day to find creators who could make the videos for a low cost.
• Scale what already works: After proving the format organically, he hired user-generated-content creators and later put paid ads behind content that had already performed well.

Reported Metrics and Economics

• Revenue: About $100,000 per month on average, according to Michael.
• Subscription pricing: $35 per year or $5 per week, plus a freemium tier.
• Downloads: About 700,000 on iOS and several hundred thousand on Android—roughly 1 million total.
• Growth milestones: Michael described reaching about $3,000 per month with his content and a few UGC creators, then around $10,000 per month after improving the paywall and scaling, and roughly $30,000 per month by month five as he tested additional formats. He then used paid ads to grow beyond $100,000 per month.
• Paywall: He reported a 91% paywall view rate; the interview does not define the denominator.
• Marketing activity: 10 TikToks per day during the initial testing period and around 50 creator DMs per day during outreach.
• Attribution cost: Singular, an MMP, reportedly cost $0.03 per install.
• Unreported figures: The interview does not provide specific CAC, conversion, retention, margin, or profit figures.

Frameworks and Actionable Takeaways

• Validate before overbuilding: Check marketplaces and existing products for evidence of demand, then confirm interest through customer behavior such as comments, DMs, and purchases.
• Use Maslow’s hierarchy of needs to assess relevance: Michael saw height prediction as connecting to self-esteem and belonging. His broader advice was to consider whether an app addresses important human needs.
• Don’t dismiss an idea just because competitors exist: Similar products can still succeed with distinct execution, positioning, or marketing.
• Run a content-testing loop: Publish frequently, identify formats that generate customer interest and downloads, then make the format easy for other creators to replicate.
• Scale channels in sequence: Validate organic content, recruit UGC creators, optimize the paywall, and then use paid ads to scale proven creatives.
• Be willing to tolerate embarrassment: Michael said building an unglamorous app and posting simple TikToks required putting aside concerns about social status and other people’s opinions.

Tools and Technology

Michael said Go Tall uses:

• Expo for iOS and Android development
• Superwall for paywalls
• Adapty to access advance payments because of Apple’s payout timing
• Singular as its mobile measurement partner (MMP)

Presenters and Sources

• Michael — Go Tall founder and interviewee; source of the business and product figures.
• Pat Walls — Starter Story host and interviewer.
• Gus — Starter Story producer, who reflected on the case after the interview.
• Starter Story — Channel and publisher of the case study.