Retell AI
Hosted voice-agent platform for phone and web calls with a component price list: voice infrastructure fee, chosen LLM per minute, chosen TTS per minute, and telephony; strong on contact-center features like batch calls, QA and branded caller ID.
Overview
Best for: Teams running production phone agents (inbound support, outbound reminders) that want contact-center features without building them.
At a glance
Latency is vendor claim (as low as 600 ms). $0.055/min voice infra includes STT; LLM and TTS priced per minute on top. 20 concurrent included, $8/month per extra. Typical $0.07-$0.31/min all-in.
Phone (Retell numbers, Twilio, Telnyx, custom SIP), web call SDK, custom LLM WebSocket
Same
Depends on chosen voice/LLM; not verified.
No verified number.
Not verified.
SOC 2 Type 1 and Type 2, HIPAA (self-serve BAA at click-agreements.retellai.com), GDPR DPA with SCCs, per Retell docs.
Features
- turn detection
- interruptions
- conversation flow builder
- knowledge base
- advanced denoising
- PII removal
- safety guardrails
- AI quality assurance
- batch calls
- branded caller ID
- SMS
- custom LLM via WebSocket
- telephony
Pricing
| What | Price | Unit |
|---|---|---|
| Retell voice infrastructure | $0.055 | per minute |
| LLM | GPT 4.1 nano $0.0032 ... GPT 4.1 mini $0.0128 ... GPT 5.4 $0.08 ... GPT 5.5 $0.16 | per minute |
| TTS | $0.015 (Retell/Minimax/Fish/Cartesia/OpenAI/Inworld); ElevenLabs Flash $0.04; Multilingual v2 $0.06; v3 $0.10 | per minute |
| Telephony | $0.015 | per minute |
| Extra concurrency | $8 | per concurrent call per month |
| Add-ons | +$0.005 each (KB, denoising, guardrails); PII +$0.01; QA $0.10 after 100 min | per minute |
| Phone number | $2.00 | per month |
Low: $0.055 infra + GPT 4.1 mini $0.0128 + $0.015 TTS + $0.015 telephony = ~$0.098 (cheaper with nano and BYO telephony). High: Retell's own top of range, e.g. GPT 5.x + ElevenLabs v3 + add-ons.
Free tier: $10 free credits.
Source: retellai.com
Setup
- Create an agent in the dashboard (single prompt or conversation flow), pick LLM and voice.
- Buy or import a number and bind the agent for inbound; or call create-phone-call for outbound.
- For web, create a web call server-side and start it with the Retell web SDK.
- Sign the BAA/DPA click-through before handling PHI.
Endpoint
POST https://api.retellai.com/v2/create-phone-callAuthentication
Authorization: Bearer <RETELL_API_KEY>
Quick start javascript
// Outbound call with Retell
const res = await fetch("https://api.retellai.com/v2/create-phone-call", {
method: "POST",
headers: {
Authorization: "Bearer " + process.env.RETELL_API_KEY,
"Content-Type": "application/json",
},
body: JSON.stringify({
from_number: "+14155550100", // a number you own in Retell
to_number: "+14155550123",
override_agent_id: "agent_xxx",
retell_llm_dynamic_variables: { customer_name: "Sam" },
idempotency_key: "appt-reminder-7781", // safe retries for 1 hour
honor_internal_dnc: true,
}),
});
console.log(res.status, await res.json()); // 201 -> call_id, call_statusWritten from the current docs. Check the vendor's SDK version before you ship.
Warnings
Silence and hold are billed
Billing runs per second for the whole call including silence and hold; set end-call-on-silence and max duration.
LLM choice dominates cost
GPT 5.5 at $0.16/min alone is 3x the infra fee; test cheaper models (4.1 mini, Gemini Flash) first.
Add-ons stack up
Knowledge base, denoising, guardrails (+$0.005 each), PII removal (+$0.01) and branded calls ($0.10/call) can add 20-40% to the per-minute rate.
Transfers continue telephony billing
After a transfer only the telephony fee continues, but it does continue.
International outbound needs your own numbers
Retell-purchased numbers support US destinations only for API outbound calls.
Plus 12 warnings that apply to all platforms and telephony APIs. See category warnings.
Limits
- 20 concurrent calls included, $8/month per extra
- Retell-purchased numbers can only dial US destinations via API create-phone-call
Models and products
| Name | Status |
|---|---|
| Pay as you go | GA |
| Enterprise | GA |
Docs and sources
Docs
Sources used
- retellai.com/pricing
- docs.retellai.com/api-references/create-phone-call
- docs.retellai.com/general/compliance
Exactly what is included in the $0.055 voice infra (STT assumed); languages list.