Retell AI review: is it the best AI phone agent platform to build on?
Answer in brief: Retell AI is our #1 AI phone agent for teams that want to build their own. It runs inbound and outbound phone agents on a stack you choose (LLM, voice and carrier) and charges pay-as-you-go from $0.07 to $0.31 per minute. You get a $10 starting credit and 20 concurrent calls included, and bringing your own SIP trunk costs nothing in telephony fees. The trade-off: you pick and pay for each component, so it takes a little setup.
Top pick for custom AI phone agents. Retell gives you published prices, per-second billing and a full calling toolkit: IVR navigation, warm handoffs and outbound campaigns. You can start without a sales call.
Independent research from Retell AI's own pages, read November 9, 2026. We did not test Retell hands-on. Latency and accuracy figures below are claims Retell publishes.
Built for real phone calls, in and out
Retell is a voice-agent platform for building phone agents that answer and dial. It includes templates, an API, webhooks, call analytics and simulation testing. On inbound calls, its agents can navigate IVR menus with DTMF, hand off warmly to a human, and let a supervisor listen live or take over. On outbound calls, Retell runs campaigns with pacing, retries and voicemail handling. Batch dials cost $0.005 each, and branded caller ID is $0.10 per outbound call.
Voice quality and latency: fast by design
Retell's homepage claims about 600ms latency, citing independent benchmarks, and a proprietary turn-taking model so the agent knows when to speak. You choose the voice. Retell, Minimax, Fish, Cartesia, OpenAI and Inworld voices cost $0.015/min. ElevenLabs Flash costs $0.04/min, and premium ElevenLabs voices go up to $0.10/min. Retell also cites a third-party Cekura benchmark of 414 Medicare-workflow calls that scored 95.7% workflow accuracy. Optional denoising (+$0.005/min) helps with noisy callers.
Telephony: bring your own carrier for free
Retell-provided Twilio or Telnyx telephony costs $0.015/min. If you bring your own SIP trunk or custom telephony, Retell charges nothing for telephony. Its elastic SIP trunk integrations cover Twilio, Telnyx and Vonage, plus a pre-built Five9 SIP trunk. NICE, Talkdesk and LiveVox connect through custom SIP (Retell lists these as unofficial). Numbers cost $2/month, or $10/month for a verified number. After a transfer, only the telephony fee keeps running.
Who Retell AI fits
- Startups, agencies and product teams building phone agents for themselves or their clients.
- Contact-center teams that want to plug AI into an existing SIP or Five9 setup.
- Healthcare and finance buyers who need HIPAA, SOC 2 Type II, GDPR or ISO 27001. Retell lists all four, plus an on-prem option.
Strengths that win deals
- Pay as you go with a $10 credit and 20 free concurrent calls. Extra concurrency is $8 per call per month.
- Per-second billing with no rounding up, and no charge for failed calls.
- A transparent, itemized price list for every model, voice and add-on.
- Retell says more than 4,000 businesses use it.
Honest drawbacks
- Your true per-minute rate depends on your stack. Knowledge base (+$0.005), guardrails (+$0.005), PII removal (+$0.01) and AI QA ($0.10/min after 100 free minutes) all add up.
- You're billed during silence and hold time.
- It needs some technical setup, and enterprise pricing isn't published.
Pricing at a glance
| Item | Published price |
|---|---|
| Voice agent, all-in range | $0.07–$0.31/min |
| Retell voice infrastructure | $0.055/min |
| Telephony (Twilio/Telnyx) | $0.015/min; BYO SIP free |
| Phone number | $2/mo ($10/mo verified) |
| Concurrency above 20 | $8 per call/month |
Sourced customer stories
Retell's customers page lists the San Antonio Spurs, Anker, Pine Park Health (which Retell says raised scheduling NPS by 38), Medical Data Systems (which Retell says handles 100% of inbound calls) and Everise (65% of calls contained, per Retell), among others.
Best alternatives
- Vapi: maximum per-component control, with provider costs passed through at no markup.
- Bland AI: one bundled per-minute rate and a low-latency in-house voice.
- Synthflow: a managed enterprise rollout instead of building it yourself.
Retell AI FAQ
How much does Retell AI cost per minute?
Voice agents cost $0.07–$0.31 per minute, depending on your model, voice and telephony. New accounts get a $10 credit.
Can I use my own phone carrier with Retell AI?
Yes. Retell charges nothing for telephony when you bring your own SIP trunk. Twilio, Telnyx, Vonage and Five9 are supported.
Does Retell AI make outbound calls?
Yes. It runs outbound campaigns with pacing, retries and voicemail handling, plus batch calling and branded caller ID.
Sources
- Retell AI pricing
- Retell AI homepage
- Retell AI customers
- Retell AI Twilio integration
- Cekura Medicare workflow benchmark
Building chat or ticket support agents too? See Best AI support agent.
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