*If using inches, enter total inches (e.g., 5'10" is 70 inches).
Sedentary (little or no exercise)
Lightly Active (exercise 1-3 days/week)
Moderately Active (exercise 3-5 days/week)
Very Active (hard exercise 6-7 days/week)
Extra Active (very hard exercise/physical job)
Please enter valid values for all fields.
Your Active Metabolic Rate (AMR):
0 Calories/day
Basal Metabolic Rate (BMR):0 Calories/day (Calories burned at complete rest)
Estimated Daily Needs for Weight Goals:
Maintain Weight: 0 cals
Mild Weight Loss (-0.25kg/week): 0 cals
Weight Loss (-0.5kg/week): 0 cals
Weight Gain (+0.5kg/week): 0 cals
How to Calculate Active Metabolic Rate
Understanding your energy needs is the foundational step in any fitness, health, or weight management journey. Your Active Metabolic Rate (AMR) represents the total number of calories your body burns in a single day, taking into account both your basic physiological functions and your physical activity level. Unlike the Basal Metabolic Rate (BMR), which only accounts for the energy used at rest, AMR gives a realistic picture of your Total Daily Energy Expenditure (TDEE).
The Difference Between BMR and AMR
It is crucial to distinguish between these two metrics to calculate your dietary needs effectively:
Basal Metabolic Rate (BMR): The number of calories required to keep your body functioning at rest (breathing, blood circulation, cell production). This usually accounts for 60-75% of your total calorie burn.
Active Metabolic Rate (AMR): Your BMR multiplied by an activity factor. This is the actual number of calories you burn moving, working, exercising, and digesting food throughout the day.
The Calculation Formula
This calculator uses the Mifflin-St Jeor Equation, widely considered by clinical professionals to be the most accurate standard formula for estimating calorie needs.
Step 1: Calculate BMR
For Men:
(10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For Women:
(10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Step 2: Calculate AMR
Once the BMR is established, it is multiplied by an Activity Factor relative to your lifestyle:
Activity Level
Multiplier
Description
Sedentary
1.2
Desk job, little to no exercise
Lightly Active
1.375
Light exercise/sports 1-3 days/week
Moderately Active
1.55
Moderate exercise/sports 3-5 days/week
Very Active
1.725
Hard exercise/sports 6-7 days/week
Extra Active
1.9
Very hard daily exercise or physical job
Example Calculation
Let's look at a realistic example of how to calculate active metabolic rate manually:
Consider a 35-year-old female who weighs 68 kg, is 165 cm tall, and works a desk job but exercises 4 days a week (Moderately Active).
To maintain her current weight, she should consume approximately 2,132 calories per day.
Using Your AMR for Weight Goals
Once you have your AMR, you can manipulate your calorie intake to achieve your goals:
Weight Loss: Consuming fewer calories than your AMR creates a calorie deficit. A deficit of 500 calories per day typically results in 0.5 kg (approx 1 lb) of weight loss per week.
Weight Gain: Consuming more calories than your AMR creates a surplus, necessary for building muscle mass. A surplus of 250-500 calories is often recommended for lean muscle gain.
Maintenance: Consuming calories equal to your AMR allows you to maintain your current body weight.
function calculateMetabolicRate() {
// 1. Get Input Values
var ageInput = document.getElementById('amr_age').value;
var weightInput = document.getElementById('amr_weight').value;
var heightInput = document.getElementById('amr_height').value;
var activityValue = document.getElementById('amr_activity').value;
// Get Units
var weightUnit = document.getElementById('amr_weight_unit').value;
var heightUnit = document.getElementById('amr_height_unit').value;
// Get Gender
var genderRadios = document.getElementsByName('amr_gender');
var genderValue = 'male'; // default
for (var i = 0; i < genderRadios.length; i++) {
if (genderRadios[i].checked) {
genderValue = genderRadios[i].value;
break;
}
}
// 2. Validate Inputs
if (ageInput === '' || weightInput === '' || heightInput === '' ||
isNaN(parseFloat(ageInput)) || isNaN(parseFloat(weightInput)) || isNaN(parseFloat(heightInput))) {
document.getElementById('amr_error').style.display = 'block';
document.getElementById('amr_result').style.display = 'none';
return;
}
document.getElementById('amr_error').style.display = 'none';
// 3. Parse and Convert Units to Metric (Kg and Cm)
var age = parseFloat(ageInput);
var weight = parseFloat(weightInput);
var height = parseFloat(heightInput);
// Convert Weight to kg if lbs
if (weightUnit === 'lbs') {
weight = weight * 0.453592;
}
// Convert Height to cm if inches
if (heightUnit === 'in') {
height = height * 2.54;
}
// 4. Calculate BMR (Mifflin-St Jeor Equation)
var bmr = 0;
if (genderValue === 'male') {
// (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
// (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// 5. Calculate AMR
var activityMultiplier = parseFloat(activityValue);
var amr = bmr * activityMultiplier;
// 6. Calculate Goals
var maintain = Math.round(amr);
var mildLoss = Math.round(amr – 250);
var stdLoss = Math.round(amr – 500);
var stdGain = Math.round(amr + 500);
// 7. Display Results
document.getElementById('bmr_display_value').innerText = Math.round(bmr).toLocaleString();
document.getElementById('amr_display_value').innerText = Math.round(amr).toLocaleString();
document.getElementById('maintain_cals').innerText = maintain.toLocaleString();
document.getElementById('loss_mild').innerText = mildLoss.toLocaleString();
document.getElementById('loss_std').innerText = stdLoss.toLocaleString();
document.getElementById('gain_std').innerText = stdGain.toLocaleString();
document.getElementById('amr_result').style.display = 'block';
}