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

# Flat Volatility Surface

> Query a flat (constant) volatility surface that returns the same volatility for any expiry and strike. Useful for testing, basic Black-Scholes pricing, or when assuming constant volatility across all options. Returns both the volatility and total variance for a given query point. [Tier: PRO, Credits: 5]



## OpenAPI

````yaml api-specs/volatility.json post /quantlib/volatility/surface/flat
openapi: 3.1.0
info:
  title: FinceptQuantLib API - Volatility
  description: >-
    Volatility module endpoints for FinceptQuantLib API. Standard Tier module (2
    credits per request) providing comprehensive volatility surface modeling,
    SABR model calibration and analytics, and local volatility calculations for
    derivatives pricing and risk management.
  version: 3.0.0
  contact:
    name: Fincept API Support
    url: https://fincept.in
servers:
  - url: https://api.fincept.in
    description: Fincept API Production Server
security:
  - APIKeyHeader: []
tags:
  - name: quantlib-volatility
    description: >-
      Volatility surface modeling, SABR calibration, and local volatility
      calculations
    x-displayName: Volatility
paths:
  /quantlib/volatility/surface/flat:
    post:
      tags:
        - quantlib-volatility
      summary: Flat Volatility Surface
      description: >-
        Query a flat (constant) volatility surface that returns the same
        volatility for any expiry and strike. Useful for testing, basic
        Black-Scholes pricing, or when assuming constant volatility across all
        options. Returns both the volatility and total variance for a given
        query point. [Tier: PRO, Credits: 5]
      operationId: flat_volatility
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - volatility
                - query_expiry
                - query_strike
              properties:
                volatility:
                  type: number
                  description: Constant volatility value (annualized, e.g., 0.20 for 20%)
                  example: 0.25
                  minimum: 0
                  maximum: 5
                query_expiry:
                  type: number
                  description: Time to expiry in years for the query point
                  example: 1
                  minimum: 0
                query_strike:
                  type: number
                  description: Strike price for the query point
                  example: 100
                  minimum: 0
            example:
              volatility: 0.25
              query_expiry: 1
              query_strike: 100
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: true
                  data:
                    type: object
                    properties:
                      volatility:
                        type: number
                        description: Volatility at the query point (same as input)
                        example: 0.25
                      total_variance:
                        type: number
                        description: Total variance (volatility^2 * time)
                        example: 0.0625
                      expiry:
                        type: number
                        description: Query expiry (echo of input)
                        example: 1
                      strike:
                        type: number
                        description: Query strike (echo of input)
                        example: 100
              example:
                success: true
                data:
                  volatility: 0.25
                  total_variance: 0.0625
                  expiry: 1
                  strike: 100
        '401':
          $ref: '#/components/responses/UnauthorizedError'
        '402':
          $ref: '#/components/responses/InsufficientTierError'
        '422':
          $ref: '#/components/responses/ValidationError'
      security:
        - APIKeyHeader: []
components:
  responses:
    UnauthorizedError:
      description: Authentication information is missing or invalid
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Invalid API key
    InsufficientTierError:
      description: API tier insufficient for this endpoint
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Endpoint requires Standard tier or higher
    ValidationError:
      description: Validation Error
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: array
                items:
                  type: object
                  properties:
                    loc:
                      type: array
                      items:
                        type: string
                    msg:
                      type: string
                    type:
                      type: string
          example:
            detail:
              - loc:
                  - body
                  - volatility
                msg: field required
                type: value_error.missing
  securitySchemes:
    APIKeyHeader:
      type: apiKey
      in: header
      name: X-API-Key
      description: >-
        API key for authentication. Get your key at
        https://api.fincept.in/auth/register

````