TDEE and Macro Calculator API: Add Calorie Needs to Any Fitness App

A TDEE calculator API (Total Daily Energy Expenditure) takes a user's age, weight, height, activity level, and goal and returns their daily calorie needs plus protein, carbohydrate, and fat targets, with no formula to implement on your side. Instead of embedding the Mifflin-St Jeor equation into every app you ship, you call one endpoint and render the result.

This guide shows how the macro calculator API works, what the response structure looks like, and how to integrate it into a React, Swift, or Python app.

Why Use an API Instead of Implementing the Formula Yourself

The Mifflin-St Jeor BMR formula is simple on its own:

BMR (male)   = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
BMR (female) = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161
TDEE         = BMR × activity_multiplier

But production apps add goal-adjusted targets, macro splits, unit conversions, edge-case validation, and versioning as nutrition science evolves. Offloading calorie needs calculation to an API keeps that logic centralised and consistent across your web, iOS, and Android clients.

The Endpoint

GET /api/v1/public/calc/macros

Parameters:

Activity levels:

Quick Start

curl "https://api.calorieapi.com/api/v1/public/calc/macros\
?age=28&gender=male&weight_kg=80&height_cm=178\
&activity=moderately_active&goal=lose"

Response:

{
  "bmr": 1778,
  "tdee": 2756,
  "activity_multiplier": 1.55,
  "daily_targets": {
    "calories": 2204,
    "protein_g": 144.0,
    "carbohydrates_g": 220.5,
    "fat_g": 61.2
  },
  "formula": "Mifflin-St Jeor"
}

The daily_targets.calories field is tdee × 0.80 for goal=lose, tdee for maintain, and tdee × 1.10 for gain. Protein is set at 1.8 g/kg for cut and bulk phases (muscle-sparing) and 1.6 g/kg for maintenance. Fat fills 25 % of goal calories; carbohydrates fill the remainder.

Integrating in JavaScript / React

async function getCalorieTargets({ age, gender, weightKg, heightCm, activity, goal }) {
  const params = new URLSearchParams({ age, gender, weight_kg: weightKg,
    height_cm: heightCm, activity, goal });
  const res = await fetch(
    `https://api.calorieapi.com/api/v1/public/calc/macros?${params}`
  );
  if (!res.ok) throw new Error(`Calc failed: ${res.status}`);
  return res.json();
}

// Display in a React component
const targets = await getCalorieTargets({
  age: 28, gender: 'male', weightKg: 80, heightCm: 178,
  activity: 'moderately_active', goal: 'lose'
});

console.log(`Daily calories: ${targets.daily_targets.calories}`);
console.log(`Protein: ${targets.daily_targets.protein_g}g`);

Integrating in Swift (iOS)

struct MacroTargets: Codable {
  let bmr: Int
  let tdee: Int
  let dailyTargets: DailyTargets

  struct DailyTargets: Codable {
    let calories: Int
    let proteinG: Double
    let carbohydratesG: Double
    let fatG: Double
  }
}

func fetchCalorieTargets(age: Int, gender: String, weightKg: Double,
                          heightCm: Double, activity: String, goal: String) async throws -> MacroTargets {
  var components = URLComponents(string: "https://api.calorieapi.com/api/v1/public/calc/macros")!
  components.queryItems = [
    .init(name: "age", value: "\(age)"),
    .init(name: "gender", value: gender),
    .init(name: "weight_kg", value: "\(weightKg)"),
    .init(name: "height_cm", value: "\(heightCm)"),
    .init(name: "activity", value: activity),
    .init(name: "goal", value: goal),
  ]
  let (data, _) = try await URLSession.shared.data(from: components.url!)
  return try JSONDecoder().decode(MacroTargets.self, from: data)
}

Displaying Results in Your UI

Map the response fields to progress bars or ring charts:

Recalculating as the User Updates Their Profile

Call the endpoint whenever the user saves a profile change. Store the returned daily_targets in your local state or database so the rest of the app can reference it without another API call.

import httpx

def get_macro_targets(profile: dict) -> dict:
    r = httpx.get("https://api.calorieapi.com/api/v1/public/calc/macros", params={
        "age": profile["age"],
        "gender": profile["gender"],
        "weight_kg": profile["weight_kg"],
        "height_cm": profile["height_cm"],
        "activity": profile["activity_level"],
        "goal": profile["goal"],
    })
    r.raise_for_status()
    return r.json()

Try It Live

The API Playground lets you enter your stats and see the full JSON response before writing a line of code.

Related Guides

• How to Build a Calorie Tracker App
• Keto Macro API: Track Net Carbs
• Food Portion Size Calculator API
• Recipe Nutrition Analyzer API

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