BMI & BMR Calculator API

What it does

BMI BMR Calculator gives you body composition and calorie estimates from basic measurements. Send weight and height to calculate BMI, category, BMI Prime, Ponderal Index, WHO class, waist-to-height ratio, and target weight values. Send weightKg, heightCm, ageYears, sex, and optional activity or bodyFatPct to calculate basal metabolic rate and daily calorie needs.

Use the /bmi endpoint when you need a quick health metric from metric or imperial inputs. It accepts weight and height as required fields, with optional waist, targetBmi, and targetBmiPrime. The response is an object, so you can map the values into your own UI, intake flow, or fitness workflow without reshaping nested records.

Use the /bmr endpoint when you need calorie planning from body measurements. It supports the Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas, plus activity levels from sedentary to very_active. When bodyFatPct is provided, the calculation can switch to Katch-McArdle, which is useful for more precise lean-mass-based estimates.

BMI BMR Calculator is a fit for wellness apps, onboarding questionnaires, health dashboards, and personal training tools that need standardized measurement-based outputs.

▣ ENDPOINT 01 / 02

POST

Calculate BMI, category, BMI Prime, Ponderal Index, WHO class, waist-to-height ratio and target weight in metric or imperial units

https://api.eu.apyhub.com/freedailypro/bmi-bmr-calculator/bmi

QUICKSTART

GUIDE

Quickstart

Calculate BMI from your weight and height with the minimum required JSON body.

curl -X POST "https://api.eu.apyhub.com/freedailypro/bmi-bmr-calculator/bmi" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"weight":54,"height":170}'

What you'll get back

Returns a JSON object. The output schema does not declare any top-level fields, so the response shape is unspecified here.

{
  "result": {
    "bmi": 18.7,
    "category": "Normal",
    "bmiPrime": 0.75,
    "ponderalIndex": 11,
    "whoClass": "Normal range",
    "whoRange": "18.5 to 24.99",
    "healthyWeightRange": {
      "lowKg": 53.5,
      "highKg": 72
    },
    "steps": [
      {
        "label": "Height in metres",
        "formula": "height in cm / 100",
        "inputs": {
          "cm": 170
        },
        "result": 1.7
      },
      {
        "label": "BMI",
        "formula": "weight in kg / (height in m)^2",
        "inputs": {
          "weight": "54.0 kg",
          "height": "1.7 m"
        },
        "result": "18.7"
      },
      {
        "label": "BMI Prime",
        "formula": "BMI / 25",
        "inputs": {
          "BMI": "18.7"
        },
        "result": "0.75"
      },
      {
        "label": "Ponderal Index",
        "formula": "weight in kg / (height in m)^3",
        "inputs": {
          "weight": "54.0 kg",
          "height": "1.7 m"
        },
        "result": "11.0 kg/m3"
      },
      {
        "label": "WHO class",
        "formula": "the WHO adult BMI table row that contains the BMI",
        "inputs": {
          "BMI": "18.7"
        },
        "result": "Normal range (18.5 to 24.99)"
      }
    ]
  }
}

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API key

Loading your default key…

The full key is used to call the gateway and stays in this tab — never sent to orbit or saved.

About this endpoint

What it does

Calculates BMI from the submitted weight and height, using metric or imperial units. The endpoint accepts optional waist and target BMI inputs, but the response schema is not yet defined in the output schema.

Request Body

Parameter	Type	Mandatory	Description
unit	ENUM	No	Allowed values: `metric`, `imperial`. Default: `metric`. Use `metric` for kg and cm, or `imperial` for lb and inches.
waist	Number	No	Optional waist measurement in cm (metric) or inches (imperial). Minimum: 0.0001. Adds the waist-to-height ratio and its band.
height	Number	Yes	Height in cm (metric) or inches (imperial). Minimum: 0.0001. Metric range: 50 to 272 cm. Imperial range: 20 to 107 in.
weight	Number	Yes	Weight in kg (metric) or pounds (imperial). Minimum: 0.0001. Metric range: 2 to 700 kg. Imperial range: 4 to 1500 lb.
targetBmi	Number	No	Optional target BMI. Minimum: 0.0001. Allowed range: 10 to 60. Adds the weight that gives it at this height and the change from now.
targetBmiPrime	Number	No	Optional target BMI Prime. Minimum: 0.0001. Target BMI Prime is target BMI divided by 25. Send this or `targetBmi`, not both.

Response

Parameter	Type	Description
result	object	Contains the BMI calculation results.
result.bmi	number	Calculated Body Mass Index (BMI).
result.category	string	BMI category (e.g., Normal).
result.bmiPrime	number	BMI Prime value.
result.ponderalIndex	number	Calculated Ponderal Index.
result.whoClass	string	WHO BMI classification.
result.whoRange	string	BMI range associated with the WHO classification.
result.healthyWeightRange	object	Contains the estimated healthy weight range in kilograms.
result.healthyWeightRange.lowKg	number	Lower limit of the healthy weight range in kg.
result.healthyWeightRange.highKg	number	Upper limit of the healthy weight range in kg.
result.steps	array	Contains the calculation steps, formulas, inputs, and intermediate results.
result.steps[].label	string	Name of the calculation step.
result.steps[].formula	string	Formula used for the calculation.
result.steps[].inputs	object	Input values used in the calculation step.
result.steps[].result	number/string	Result of the calculation step.

▣ ENDPOINT 02 / 02

POST

Calculate basal metabolic rate and daily calories from body measurements and activity

https://api.eu.apyhub.com/freedailypro/bmi-bmr-calculator/bmr

QUICKSTART

GUIDE

Quickstart

Calculate your BMR from weight, height, age, and sex with a single request.

curl -X POST "https://api.eu.apyhub.com/freedailypro/bmi-bmr-calculator/bmr" \
  -H "apy-token: $APY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "weightKg": 54,
    "heightCm": 170,
    "ageYears": 25,
    "sex": "male"
  }'

What you'll get back

Returns a JSON object.

{
  "result": {
    "bmr": 1483,
    "tdee": 2298,
    "activity": "moderate"
  }
}

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API key

Loading your default key…

The full key is used to call the gateway and stays in this tab — never sent to orbit or saved.

About this endpoint

What it does

Calculates basal metabolic rate from the body measurements in the request body. The endpoint accepts the user’s sex, age, height, and weight, with optional formula, activity, and body fat percentage inputs.

Request Body

Parameter	Type	Mandatory	Description
sex	ENUM	Yes	Allowed values: `male`, `female`.
formula	ENUM	No	Equation to use. Allowed values: `mifflin-st-jeor`, `harris-benedict`, `katch-mcardle`. Default: `mifflin-st-jeor` (or `katch-mcardle` when `bodyFatPct` is sent). `harris-benedict` is the 1984 Roza-Shizgal revision. `katch-mcardle` needs `bodyFatPct`.
activity	ENUM	No	Allowed values: `sedentary`, `light`, `moderate`, `active`, `very_active`.
ageYears	Number	Yes	Age in years. Minimum: `0.0001`; maximum: `120`.
heightCm	Number	Yes	Height in centimeters. Minimum: `0.0001`.
weightKg	Number	Yes	Weight in kilograms. Minimum: `0.0001`.
bodyFatPct	Number	No	Body fat as a percentage. Description notes a range of `3` to `60` and that it switches to Katch-McArdle (`370 + 21.6 x lean body mass in kg`) unless `formula` says otherwise.

Response

Parameter	Type	Description
result	object	Contains the BMR and TDEE calculation results.
result.bmr	number	Calculated Basal Metabolic Rate (BMR), representing the estimated calories burned at rest per day.
result.tdee	number	Calculated Total Daily Energy Expenditure (TDEE), representing the estimated daily calories burned based on activity level.
result.activity	string	Activity level used for the calculation (e.g., moderate).

▣ COMMON ERRORS

Errors any endpoint can return

400bad_request

Required parameter missing or malformed body.

401unauthorized

API key missing, revoked, or not authorized for this service.

429rate_limited

Your plan's per-second rate exceeded. Retry with exponential backoff.

503upstream_busy

Backend temporarily unavailable. Try again in a few seconds.

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