Henry Langmack

Henry Langmack is a US-based teenage developer best known as the co-founder and chief technology officer of Cal AI, the AI calorie tracker that estimates a meal's nutrition from a photo. Langmack and Zach Yadegari started Cal AI as 17-year-old high-school students in 2024, grew it to more than 15 million downloads and over $30 million in annual revenue, and sold it to MyFitnessPal in March 2026.

Langmack met Yadegari at a coding camp at age 10. Through their teens the pair kept shipping small apps together, with the plan of releasing one after another until something clearly took off and then going all in. Langmack attended Princeton High School while building.

Cal AI launched in May 2024, with app maker Blake Anderson as a third co-founder and Jake Castillo running influencer marketing. As CTO, Langmack led the technical side of an app built on models from OpenAI and Anthropic, designed to be simple enough to understand within a few seconds of a TikTok video. The team stayed tiny, with about seven employees at the time of the sale, while the app was marketed almost entirely through creators. By March 2025 it had passed 5 million downloads, and Forbes put the company on its 2026 30 Under 30 list.

MyFitnessPal announced the acquisition on March 2, 2026, citing more than $40 million in sales over the previous year; terms were not disclosed. Langmack started at New York University in September 2025 and, after the exit, co-founded Rift, a web app for finding and booking cheap flights with fare alerts and trip management, and Soar, according to profiles on X and LinkedIn.

Langmack is one of the clearest examples of the new generation of teenage builders who used AI APIs and TikTok distribution to build a large consumer business before finishing school.