$11M/year Calendly for AI voice agents
Jan-Erik Asplund
TL;DR: Cal.com launched as an open-source Calendly alternative and is expanding into scheduling infrastructure for enterprises, marketplaces & AI agents as basic booking links become bundled software features. Sacra estimates Cal.com hit $11M annual recurring revenue (ARR) in September 2026, up from $6.2M at the end of 2025 (+111% YoY in 2025). For more, check out our full report and dataset on Cal.com.
As AI agents began to pervade support (Sierra, Decagon), we researched speech-to-text (Deepgram), text-to-speech (ElevenLabs, Cartesia), and the platforms (Retell AI, Vapi) that put it all together to power these agents on the backend.
Now, we're looking at Cal.com, the scheduling infrastructure that lets them check availability & book a time.
Key points via Sacra AI:
- Calendly (2013) turned the back-and-forth of finding a meeting time into a shareable booking link, establishing scheduling as a standalone software business and creating the opening for Cal.com (2021, originally Calendso) to launch as an open-source alternative that developers could self-host, customize & embed into their own products. Cal.com’s open source model paired free, self-hosted scheduling software with paid hosting, enterprise features & a managed Platform API, charging companies via with API usage fees tied to booking volume rather than based on seats.
- With Google Calendar & Microsoft 365 incorporating appointment booking and HubSpot offering a free scheduler inside its CRM, the booking link that helped Calendly reach $349M ARR at the end of 2024 (+40% YoY) with SMBs has increasingly become a feature of bundled productivity suites that businesses already pay for. In turn, Cal.com focused upmarket on complex enterprise & embedded deployments like at its customer Deel which needs to route bookings across teams, apply their own rules & keep users inside its app alongside an April 2026 move to proprietary production code while retaining an open-source community edition, Cal.diy.
- As AI agents increasingly handle incoming calls for businesses, scheduling provides a customer-facing interface & embedded booking for voice-agent platforms like Retell AI, with Sacra estimating it hit $11M annual recurring revenue (ARR) in September 2026, up from $6.2M at the end of 2025 (+111% YoY in 2025). To provide a human feel to scheduling and reduce no shows, its native voice agent Cal.ai ($0.29/minute) offers a scheduling assistant that automates appointment follow ups & confirmations, with built-in payment collection that lets providers charge for booked sessions.
For more, check out this other research from our platform:
