Understanding CPS and Concurrent Call Limits in Twilio – Twilio Support

Overview

When building voice applications with Twilio, it’s important to understand the concepts of Calls Per Second (CPS) and concurrent calls. These two terms are often confused, but they play distinct roles in how your Twilio-powered communications scale and perform.

Product

Programmable Voice & Elastic SIP Trunking

Frequently Asked Questions

What is CPS (Calls Per Second)?

CPS refers to the number of new calls Twilio can initiate or process per second for your account. This rate is determined by the CPS limit set on your account. By default, each Twilio account can make 1 outgoing call per second. This limit applies to both Outbound API-requested Programmable Voice calls and Elastic SIP Trunking calls.

What are Concurrent Calls?

Concurrent calls represent the total number of calls that are currently active, in progress, or live on your account at any given moment. Unlike CPS, which is about the rate of new call initiation, concurrent calls measure the volume of ongoing calls. With an approved Business Customer Profile, you can have as many concurrent calls as your infrastructure supports, subject to Twilio’s policies.

Conclusion

Key Differences Between CPS and Concurrent Calls

CPS (Calls Per Second): The rate at which new calls can be processed per second.
Concurrent Calls: The total number of calls that are active in a Twilio account.

Default Limits and How to Increase CPS

By default, Twilio accounts are limited to 1 outgoing call per second. If your project requires higher outbound call throughput, you can request an increase to your CPS limit directly from the Twilio Console:

Programmable Voice and Client: Set CPS in the "Calls per Second" section on the Voice Setting page.
Elastic SIP Trunking: Set CPS per region in the "Calls per Second" section of your trunk's Termination settings page

How to Decrease CPS

If existing CPS is between 1 to 5-:

You can decrease using self-serve options in console.

If the existing CPS value is above 5-:

Kindly contact support to decrease CPS.

Note: Decreasing CPS values can only be made for the 1st day of the month. The decrease occurs automatically on the 1st day of the month, and therefore, should be scheduled in advance to avoid any delay in the decrease (i.e. if you wait until the 1st of the month, it's possible the change will not take effect until the 1st day of the following month).

Note: If a SIP Trunk is deleted, the CPS is not deleted automatically. Please contact support if CPS on a deleted SIP Trunk needs to be deleted.