Name: Fitness Calculator API: BMI, TDEE, Macros, Body Fat
Brand: tidydata
SKU: api-tidydata-health-calculator
Availability: InStock
Author: API Market

TidyData

# Fitness Calculator API

## Overview

The Fitness Calculator API bundles six standard health calculators behind GET endpoints under /v1/health. /bmi returns the BMI value, its category and a healthy weight range for the given height. /bmr returns basal metabolic rate with the Mifflin-St Jeor formula, /calories multiplies it by an activity factor to give TDEE and calorie targets to lose, maintain or gain, and /macros turns a goal into daily protein, fat and carb grams with a percentage split. /ideal-weight compares the Devine, Robinson, Miller and Hamwi formulas and averages them, and /body-fat estimates body fat percentage with the U.S. Navy circumference method.

It is designed for fitness and diet apps, gym and coaching platforms, health content sites, chatbots and onboarding questionnaires that need consistent numbers without implementing and testing each formula. Every endpoint accepts metric (kg and cm) or imperial (lb and inches) input through the units parameter, and responses name the formula used. Results are for information only, not medical advice. Buyers only need the x-api-market-key header.

## Features

*   **6 endpoints**: BMI, BMR, daily calories (TDEE), macros, ideal weight and body fat.
*   **Published formulas**: Mifflin-St Jeor for BMR, Devine, Robinson, Miller and Hamwi for ideal weight, and the U.S. Navy method for body fat.
*   **Goal based targets**: Calories returns lose, maintain and gain targets, and macros returns grams and percentage split for a chosen goal.
*   **Activity levels**: Choose sedentary, light, moderate, active or very_active for TDEE and macros.
*   **Metric or imperial**: Send kg and cm, or lb and inches with units=imperial.
*   **10 requests per second**: All plans allow up to 10 requests per second.

## Use Cases

*   **Fitness and diet apps**: Show BMI, calorie targets and macro splits on a user's profile after signup.
*   **Coaching platforms**: Personal trainers can generate a starting calorie and macro plan for each client.
*   **Onboarding questionnaires**: Health and meal kit services can turn quiz answers into personalized calorie goals.
*   **Health content sites**: Publishers can add interactive BMI, ideal weight and body fat calculators to articles.
*   **Chatbots**: Wellness bots can answer how many calories a user needs with one API call.

## API Documentation

### Base URL

All requests go through the API.market gateway at this base URL:

```
https://prod.api.market/api/v1/tidydata/health-calculator
```

### Authentication

Every request needs your API.market key in the `x-api-market-key` header:

```
x-api-market-key: YOUR_API_KEY
```

Replace `YOUR_API_KEY` with your actual API key.

### Endpoints

#### 1. Calculate BMI

Returns BMI, the weight category and the healthy weight range in kg for the given weight and height. Intended as an adult screening measure.

**Method:** `GET`

**Endpoint:** `/v1/health/bmi`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `weight` | query | Weight (kg, or lb if units=imperial) | string | Yes | - | - |
| `height` | query | Height (cm, or inches if units=imperial) | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/bmi?weight=70&height=175&units=metric" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "bmi": 22.9,
  "category": "Normal weight",
  "healthyWeightRangeKg": [
    56.7,
    76.3
  ],
  "note": "BMI is a screening measure for adults, not a diagnosis."
}
```

#### 2. Calculate BMR

Returns basal metabolic rate in kcal per day using the Mifflin-St Jeor formula from weight, height, age and sex.

**Method:** `GET`

**Endpoint:** `/v1/health/bmr`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `weight` | query | Weight (kg, or lb if units=imperial) | string | Yes | - | - |
| `height` | query | Height (cm, or inches if units=imperial) | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |
| `age` | query | Age in years | string | Yes | - | - |
| `sex` | query | male or female | string | Yes | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/bmr?weight=70&height=175&units=metric&age=30&sex=male" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "bmrKcal": 1649,
  "formula": "Mifflin-St Jeor"
}
```

#### 3. Calculate daily calories (TDEE)

Returns BMR, total daily energy expenditure for the chosen activity level, and calorie targets to lose, maintain or gain weight.

**Method:** `GET`

**Endpoint:** `/v1/health/calories`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `weight` | query | Weight (kg, or lb if units=imperial) | string | Yes | - | - |
| `height` | query | Height (cm, or inches if units=imperial) | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |
| `age` | query | Age in years | string | Yes | - | - |
| `sex` | query | male or female | string | Yes | - | - |
| `activity` | query | sedentary, light, moderate, active, very_active | string | No | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/calories?weight=70&height=175&units=metric&age=30&sex=male&activity=moderate" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "bmrKcal": 1649,
  "tdeeKcal": 2556,
  "activity": "moderate",
  "goals": {
    "lose": 2056,
    "maintain": 2556,
    "gain": 2856
  },
  "formula": "Mifflin-St Jeor x activity factor"
}
```

#### 4. Calculate macros for a goal

Returns the daily calorie target for the goal (lose, maintain or gain) with protein, fat and carb grams and their percentage split.

**Method:** `GET`

**Endpoint:** `/v1/health/macros`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `weight` | query | Weight (kg, or lb if units=imperial) | string | Yes | - | - |
| `height` | query | Height (cm, or inches if units=imperial) | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |
| `age` | query | Age in years | string | Yes | - | - |
| `sex` | query | male or female | string | Yes | - | - |
| `activity` | query | Activity level | string | No | - | - |
| `goal` | query | lose, maintain or gain | string | No | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/macros?weight=70&height=175&units=metric&age=30&sex=male&activity=moderate&goal=lose" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "goal": "lose",
  "calories": 2056,
  "macros": {
    "proteinG": 140,
    "fatG": 57,
    "carbsG": 246
  },
  "split": {
    "protein": 27.2,
    "fat": 25,
    "carbs": 47.9
  }
}
```

#### 5. Calculate ideal weight

Returns ideal weight in kg from the Devine, Robinson, Miller and Hamwi formulas plus their average, from height and sex.

**Method:** `GET`

**Endpoint:** `/v1/health/ideal-weight`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `height` | query | Height (cm or inches) | string | Yes | - | - |
| `sex` | query | male or female | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/ideal-weight?height=175&sex=female&units=metric" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "idealWeightKg": {
    "devine": 66,
    "robinson": 64.1,
    "miller": 65.2,
    "hamwi": 65.1
  },
  "averageKg": 65.1
}
```

#### 6. Estimate body fat

Returns body fat percentage with the U.S. Navy circumference method from height, neck and waist, plus hip for women.

**Method:** `GET`

**Endpoint:** `/v1/health/body-fat`

**Parameters:**

| Name | In | Description | Type | Required | Default | Max Value |
|---|---|---|---|---|---|---|
| `height` | query | Height | string | Yes | - | - |
| `neck` | query | Neck circumference | string | Yes | - | - |
| `waist` | query | Waist circumference | string | Yes | - | - |
| `hip` | query | Hip circumference (female only) | string | No | - | - |
| `sex` | query | male or female | string | Yes | - | - |
| `units` | query | metric or imperial | string | No | - | - |

**Example Request:**

```bash
curl -X GET "https://prod.api.market/api/v1/tidydata/health-calculator/v1/health/body-fat?height=175&neck=38&waist=82&hip=&sex=male&units=metric" \
  -H "x-api-market-key: YOUR_API_KEY"
```

**Example Response (200 OK):**

```json
{
  "bodyFatPercent": 14.5,
  "method": "U.S. Navy circumference method"
}
```

## Status Codes

| Code | Status | Description |
|---|---|---|
| 200 | OK | The request succeeded and the result is in the response body. |
| 400 | Bad Request | A required parameter is missing or a value is invalid. The body explains the problem. |
| 401 | Unauthorized | The `x-api-market-key` header is missing, invalid or expired. |
| 403 | Forbidden | Your subscription does not include this endpoint. |
| 404 | Not Found | The requested item or path does not exist. |
| 429 | Too Many Requests | You went over 10 requests per second or used up your plan quota. |
| 500 | Internal Server Error | Something failed while processing the request. Retry after a short delay. |

## Rate Limits

Every plan allows 10 requests per second. The Pro plan includes 25,000 calls a month and the Ultra plan 150,000; when a monthly quota is used up, further calls return `429 Too Many Requests` until the next billing period. The pay-as-you-go plan has no quota and bills US$0.0005 per successful call. If you receive a `429`, back off before retrying and honour any `Retry-After` header.

## FAQ

**Which units does the API accept?**

Set units=metric to send weight in kg and height and circumferences in cm, or units=imperial to send weight in lb and lengths in inches.

**Which activity levels can I use?**

sedentary, light, moderate, active and very_active. The activity level is used by /v1/health/calories and /v1/health/macros.

**Do I need the hip measurement for body fat?**

Only for women. The U.S. Navy method uses height, neck and waist for men, and height, neck, waist and hip for women.

**Which formulas are used?**

BMR uses Mifflin-St Jeor, TDEE multiplies BMR by an activity factor, ideal weight returns Devine, Robinson, Miller and Hamwi with an average, and body fat uses the U.S. Navy circumference method. Each response names its formula or method.

**Can I use the results as medical advice?**

No. The calculators are for information only. The BMI response itself notes that BMI is a screening measure for adults, not a diagnosis.

**How much does it cost?**

There is no free plan. Pay as you go costs US$0.0005 per call with no monthly fee. Pro is US$4.99 per month for 25,000 calls and Ultra is US$14.99 per month for 150,000 calls. Every plan allows 10 requests per second.

## Contact Us

If you have any questions or need assistance, you can reach out to us through the embedded chat on the bottom right corner of the page or send an email to hello@magicapi.com.


Fitness calculator API for BMI with healthy weight range, BMR, TDEE calorie targets, macros, ideal weight by 4 formulas and Navy body fat, metric or imperial.