Retell AI · Rate Limits

Retell Ai Rate Limits

Retell rate-limits primarily through concurrent call entitlements: 20 free concurrent calls with each additional concurrency slot priced at $8/month. Knowledge bases get the first 10 free. Per-RPS HTTP rate limits are not publicly documented.

4 Limits Throttle: 429
AIVoiceAgentsRealtimeConversationalRate LimitingQuotasThrottling

Limits

Concurrent Calls (free tier) account
concurrent_calls
20
20 free concurrent calls included by default.
Concurrent Calls (add-on) account
concurrent_calls
-1
Additional concurrency at $8.00/concurrency/month.
Knowledge Bases (free) account
knowledge_bases
10
First 10 knowledge bases free.
HTTP Requests account
requests
not publicly documented
Verify with Retell support; standard 429 backoff applies.

Policies

Backoff Strategy
Clients should implement exponential backoff with jitter and honor any Retry-After header.
Concurrency Provisioning
Pre-purchase concurrency slots ahead of high-volume campaigns to avoid throttling.

Sources