> ## Documentation Index
> Fetch the complete documentation index at: https://developers.criteo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# /2026-01/marketing-solutions/audiences/estimate-size

> Gets the size estimation of a non existent audience. An error is returned when size calculation is not supported.



## OpenAPI

````yaml https://api.criteo.com/2026-01/marketingsolutions/open-api-specifications.json post /2026-01/marketing-solutions/audiences/estimate-size
openapi: 3.0.1
info:
  title: Criteo API
  description: Criteo API - MarketingSolutions
  version: 2026-01
servers:
  - url: https://api.criteo.com
security:
  - oauth: []
tags:
  - name: Advertiser
  - name: Analytics
  - name: Audience
  - name: Campaign
  - name: Creative
  - name: Gateway
  - name: Reco
paths:
  /2026-01/marketing-solutions/audiences/estimate-size:
    post:
      tags:
        - Audience
      summary: /2026-01/marketing-solutions/audiences/estimate-size
      description: >-
        Gets the size estimation of a non existent audience. An error is
        returned when size calculation is not supported.
      operationId: EstimateAudiencesSizes
      requestBody:
        description: ''
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/AudienceEstimateSizeInputV1'
        required: true
        x-bodyName: request
      responses:
        '200':
          description: Success or partial success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/AudienceSizeEstimationV1Response'
      security:
        - oauth:
            - MarketingSolutions_Audience_Manage
components:
  schemas:
    AudienceEstimateSizeInputV1:
      type: object
      properties:
        data:
          $ref: '#/components/schemas/AudienceEstimateSizeEntityV1Resource'
      description: Input to estimate the size of an audience.
    AudienceSizeEstimationV1Response:
      type: object
      properties:
        data:
          $ref: '#/components/schemas/AudienceSizeEstimationV1Resource'
        errors:
          type: array
          items:
            $ref: '#/components/schemas/CommonProblem'
          nullable: true
          readOnly: true
        warnings:
          type: array
          items:
            $ref: '#/components/schemas/CommonProblem'
          nullable: true
          readOnly: true
      description: >-
        A top-level object that encapsulates a Criteo API response for a single
        value
    AudienceEstimateSizeEntityV1Resource:
      type: object
      properties:
        attributes:
          $ref: '#/components/schemas/AudienceEstimateSizeEntityV1'
        type:
          type: string
      description: >-
        A top-level object that encapsulates a Criteo API response for a single
        value
    AudienceSizeEstimationV1Resource:
      type: object
      properties:
        attributes:
          $ref: '#/components/schemas/AudienceSizeEstimationV1'
        type:
          type: string
          nullable: true
      description: >-
        A top-level object that encapsulates a Criteo API response for a single
        value
      nullable: true
    CommonProblem:
      type: object
      properties:
        code:
          type: string
          description: A machine-readable error code, expressed as a string value.
          nullable: true
        detail:
          type: string
          description: >-
            A human-readable explanation specific to this occurrence of the
            problem
          nullable: true
        instance:
          type: string
          description: A URI that identifies the specific occurrence of the problem.
          nullable: true
        source:
          type: object
          additionalProperties:
            type: string
          description: >-
            A machine-readable structure to reference to the exact location(s)
            causing the error(s)
          nullable: true
        stackTrace:
          type: string
          nullable: true
        title:
          type: string
          description: A short human-readable description of the problem type
          nullable: true
        traceId:
          type: string
          description: The request correlation ID this problem comes from.
          nullable: true
        traceIdentifier:
          type: string
          description: >-
            The request correlation ID this problem comes from. (deprecated, use
            traceId instead)
          nullable: true
        type:
          enum:
            - unknown
            - access-control
            - authentication
            - authorization
            - availability
            - deprecation
            - quota
            - validation
          type: string
          description: The problem's category.
          nullable: true
      description: Common problem object.
    AudienceEstimateSizeEntityV1:
      required:
        - advertiserId
        - algebra
      type: object
      properties:
        advertiserId:
          type: string
          description: Advertiser associated to the audience
        algebra:
          $ref: '#/components/schemas/AlgebraNodeV1'
      description: Audience of people of interest for a marketer.
    AudienceSizeEstimationV1:
      type: object
      properties:
        size:
          type: integer
          format: int64
          nullable: true
      description: Audience size estimation
      nullable: true
    AlgebraNodeV1:
      type: object
      properties:
        and:
          type: array
          items:
            $ref: '#/components/schemas/AlgebraNodeV1'
          nullable: true
        audienceSegmentId:
          type: string
          nullable: true
        not:
          $ref: '#/components/schemas/AlgebraNodeV1'
        or:
          type: array
          items:
            $ref: '#/components/schemas/AlgebraNodeV1'
          nullable: true
      description: Node in the audience algebra definition.
      nullable: true
  securitySchemes:
    oauth:
      type: oauth2
      flows:
        clientCredentials:
          tokenUrl: https://api.criteo.com/oauth2/token
          scopes: {}
        authorizationCode:
          authorizationUrl: https://api.criteo.com/oauth2
          tokenUrl: https://api.criteo.com/oauth2/token
          scopes: {}

````