# Capacity groups

Capacity groups let multiple DID numbers use shared flat-rate channels, metered channels, or both. Use Capacity groups
when Capacity should be allocated to a set of DID numbers instead of reserved directly for one DID number.

## What capacity groups are

A Capacity group is created in a Capacity pool and assigned to DID numbers from **Phone Numbers > My Numbers**. DID
numbers assigned to the same group can use the group's shared channels and metered channels when those resources are
available according to Capacity priority.

Capacity groups are required for shared channels and metered channels. Dedicated channels are assigned directly to DID
numbers and do not use Capacity groups.

## Why capacity groups exist

Capacity groups make shared allocation possible. Without a group, Capacity can only be assigned directly to individual
DID numbers as dedicated channels or provided through channels included with the DID number service.

Groups are useful when several DID numbers need access to extra inbound call Capacity, but not every DID number needs a
separately reserved channel amount. They also make it possible to combine shared flat-rate channels with metered
channels so a group can use fixed monthly Capacity first and usage-based Capacity as overflow.

```
        flowchart LR

   A["Incoming call"] --> B["DID number 1"]
   A --> C["DID number 2"]
   A --> D["DID number 3"]

   B --> E["Capacity group"]
   C --> E
   D --> E

   E --> F["Shared channels"]
   F -->|if shared channels are exhausted| G["Metered channels"]
   F --> H["Destination PSTN"]
   G --> H

   class A customerAction
   class B,C,D customerAction
   class E staffAction
   class F status
   class G status
   class H reviewComplete

   classDef customerAction stroke:#38bdf8,fill:#e0f2fe,stroke-width:2px,color:#1f2d3d
   classDef status stroke:#fb923c,fill:#fee2e2,stroke-width:2px,color:#1f2d3d
   classDef staffAction stroke:#facc15,fill:#fef3c7,stroke-width:2px,color:#1f2d3d
   classDef reviewComplete stroke:#2dd4bf,fill:#ccfbf1,stroke-width:2px,color:#1f2d3d
```

## Shared channel allocation

Shared channels are flat-rate channels assigned to a Capacity group. The group can use shared channels when unassigned
flat-rate channels are available in the selected pool.

When a DID number in the group reaches its included and dedicated channel limits, additional calls can use the group's
shared channels if they are available.

Shared channels are consumed by inbound calls from DID numbers assigned to the group. A shared channel is not
permanently reserved for one DID number inside the group; it is available to the group as a shared resource while it is
not already in use.

Shared channels are limited by the number of unassigned flat-rate channels available in the selected Capacity pool. To
assign or unassign shared channels, see [Manage shared channels](how-to-guides/manage-shared-channels.html).

## Metered channel allocation

Metered channels are pay-per-minute channels assigned to a Capacity group. They can be used alone or with shared
channels in the same group.

Metered channels are used after higher-priority Capacity resources are unavailable. For priority behavior, see [Capacity
priority](capacity-reference.html#capacity-priority-values).

Metered channel allocation defines how many concurrent inbound calls can use pay-per-minute Capacity through the group.
A Capacity group can have up to 1,000 metered channels. It does not reserve flat-rate channels or create a fixed monthly
channel charge.

To assign or unassign metered channels, see [Manage metered channels](how-to-guides/manage-metered-channels.html).

## Group behavior

Capacity groups belong to a selected Capacity pool. The pool determines the countries, pricing, and available channel
resources that can be used by the group.

A group can contain shared channels, metered channels, or both. When both are configured, shared flat-rate channels are
used before metered channels. This allows predictable traffic to use fixed monthly Capacity while metered Capacity
remains available for overflow.

DID numbers must be assigned to the group before they can use the group's Capacity. Removing a DID number from a group
stops that DID number from using the group's shared or metered channels.

## Group limits

Capacity groups have channel allocation limits and DID number eligibility requirements. At least one shared or metered
channel must be assigned when creating or editing a Capacity group, and only DID numbers that support additional
Capacity can be assigned to a group.

## Related resources

- [Create a Capacity group](how-to-guides/create-capacity-group.html) - Create a group for shared channels, metered channels, or both.
- [Edit a Capacity group](how-to-guides/edit-capacity-group.html) - Rename a group or change assigned shared and metered channels.
- [Manage DID(s) in a Group](how-to-guides/manage-dids-in-group.html) - Assign or remove DID numbers directly inside a Capacity group.
- [Delete a Capacity group](how-to-guides/delete-capacity-group.html) - Delete a group that is no longer needed.
- [Assign DID numbers to a capacity group](../my-numbers/how-to-guides/assign-dids-to-capacity-group.html) - Assign DID numbers to a Capacity group from My Numbers.
- [Unassign DID numbers from a capacity group](../my-numbers/how-to-guides/unassign-dids-from-capacity-group.html) - Remove DID numbers from a Capacity group from My Numbers.
- [Capacity reference](capacity-reference.html) - Look up Capacity fields, values, and limits.

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