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Cal.ai vs Retell AI

Two fact sheets from our own research, side by side — pricing, platforms, API access and status re-checked by us rather than quoted from the vendors. Cal.ai starts at $0.29, Retell AI at $0.07. Only Retell AI has a free tier. Both ship a public API.

Cal.aiAI phone agents from Cal.com that call to book, confirm, and follow up on meetings.Retell AIBuild and run AI phone agents that book, qualify and transfer calls, billed by the minute.

Side by side

FactCal.aiRetell AI
CategoryMeeting SchedulingVoice Agents & Phone AI
Pricing modelPaidFreemium
Starts at$0.29 minute$0.07 minute
Public APIYesYes
PlatformsWeb, APIWeb, API
CompanyCal.com, Inc.Retell AI Inc.
Launched—2023
Last verifiedSep 1, 2026Sep 6, 2026

What our research says

Cal.ai

Cal.ai replaces a human caller with an AI voice agent that actually dials out or answers to get a meeting on the calendar, a step beyond typical link-based scheduling tools. Because it bills per minute on top of a Cal.com plan, costs scale directly with call volume, and it makes most sense for teams already running calendar operations through Cal.com.

Pros

  • Handles outbound and inbound calls to book, confirm, and follow up on meetings
  • Integrates directly with existing Cal.com calendar workflows
  • Team and organization plans include a monthly credit allowance

Cons

  • Per-minute billing means costs are unpredictable at high call volume
  • Requires an underlying Cal.com subscription, so it's not a stand-alone tool
  • No free allotment beyond bundled plan credits

Retell AI

One of the more honest voice-agent stacks: the pricing page breaks out infrastructure, TTS and LLM cost per minute so you can predict a call's cost instead of guessing. Telephony choice is wide and the concurrency allowance is generous. The catch is that per-minute billing plus add-ons makes a busy contact centre expensive fast, and the cheap end of the range only holds if you pick the cheap models.

Pros

  • Per-minute cost broken down by voice infrastructure, TTS provider and LLM on the public pricing page
  • Telephony via SIP trunking, Twilio and Vonage plus n8n, HubSpot, Make and Go High Level integrations
  • 20 concurrent calls included before any concurrency charge
  • Voice, chat and SMS agents share one platform and API
  • HIPAA path exists via a signed BAA covered in the terms of service

Cons

  • Cost per minute more than quadruples between the cheapest and most capable model combinations
  • Knowledge base, denoising, PII removal and branded caller ID are all metered extras
  • No flat-rate plan, so a spike in call volume lands straight on the invoice

Which one fits

Choose Cal.ai if you need

  • Sales teams doing outbound meeting booking by phone
  • Healthcare or service front desks confirming appointments
  • Teams already on Cal.com wanting to add voice

Choose Retell AI if you need

  • Teams replacing an outbound qualification or booking script
  • Contact centres that already have Twilio, Vonage or SIP trunking
  • Developers who want per-minute cost visibility before launch

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