Calculate your BMR and TDEE in Calories and Kilojoules (kJ)
Male
Female
Sedentary (little or no exercise)
Lightly Active (light exercise 1-3 days/week)
Moderately Active (moderate exercise 3-5 days/week)
Very Active (hard exercise 6-7 days/week)
Extra Active (very hard exercise & physical job)
Energy required to maintain current weight based on activity.
Goal Estimates (Daily Intake)
Weight Loss (0.5kg/week):0 Cal / 0 kJ
Weight Gain (0.5kg/week):0 Cal / 0 kJ
Understanding Your Metabolic Rate in Australia
Whether you are training in Melbourne, working in a Sydney office, or living an active lifestyle in Queensland, understanding your metabolic rate is the foundational step toward managing your weight and health. This Australian Metabolic Rate Calculator helps you estimate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the metric system (kilograms and centimetres) and provides results in both Calories and Kilojoules (kJ), aligning with Australian food labelling standards.
What is BMR (Basal Metabolic Rate)?
Your Basal Metabolic Rate (BMR) represents the number of calories or kilojoules your body burns while performing basic life-sustaining functions. Even if you stayed in bed all day, your body requires energy for:
Breathing
Circulating blood
Controlling body temperature
Cell growth and repair
BMR typically accounts for 60% to 75% of the total calories you burn each day. Our calculator uses the Mifflin-St Jeor equation, which is widely considered the most accurate formula for estimating BMR in clinical settings.
What is TDEE (Total Daily Energy Expenditure)?
While BMR is what you burn at rest, your TDEE accounts for your activity level. This includes everything from walking to the bus stop to intense gym sessions. To calculate this, we multiply your BMR by an activity factor ranging from sedentary (office work, low movement) to extra active (physical labor, athletic training).
Your TDEE is your "maintenance" number. If you consume this amount of energy daily, your weight should remain stable.
Kilojoules vs. Calories: The Australian Standard
In Australia, nutrition information panels on food products are legally required to list energy in Kilojoules (kJ). However, many people still "count calories."
The conversion rate is: 1 Calorie = 4.184 Kilojoules.
An average adult Australian diet is approximately 8,700 kJ (roughly 2,000 Calories) per day, though this varies significantly based on height, weight, age, and gender. This calculator provides both figures to make it easier for you to track your intake regardless of which unit you prefer.
How to Use These Numbers
To Lose Weight: Create a caloric deficit. A standard recommendation is to eat approximately 2,000 to 2,500 kJ (500 Calories) less than your TDEE daily to lose roughly 0.5kg per week.
To Gain Muscle: Create a surplus. Eat 1,000 to 2,000 kJ (250-500 Calories) above your TDEE, combined with resistance training.
To Maintain Weight: Aim to match your daily intake to your TDEE.
Note: These figures are estimates. Hormones, medication, and body composition (muscle vs. fat mass) also play roles in your actual metabolic rate. Always consult with an Australian GP or an Accredited Practising Dietitian (APD) before making drastic changes to your diet.
function calculateMetabolism() {
// 1. Get input values
var gender = document.getElementById("gender").value;
var age = parseInt(document.getElementById("age").value);
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var activityLevel = parseFloat(document.getElementById("activity").value);
// 2. Validate inputs
if (isNaN(age) || isNaN(weight) || isNaN(height) || age < 10 || weight < 20 || height < 100) {
alert("Please enter valid metrics. Age must be 10+, Weight 20kg+, Height 100cm+.");
return;
}
// 3. Calculate BMR (Mifflin-St Jeor Equation)
// Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
// Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
var bmr = 0;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// 4. Calculate TDEE
var tdee = bmr * activityLevel;
// 5. Convert to Kilojoules (1 Cal = 4.184 kJ)
var bmrKj = bmr * 4.184;
var tdeeKj = tdee * 4.184;
// 6. Calculate Goal Estimates (+/- 500 Calories for 0.5kg weight change/week)
var deficitCal = 500;
var deficitKj = deficitCal * 4.184;
var lossCal = tdee – deficitCal;
var lossKj = tdeeKj – deficitKj;
var gainCal = tdee + deficitCal;
var gainKj = tdeeKj + deficitKj;
// Safety check for low calories (minimum 1200 rule generally)
if (lossCal < 1200) {
// Just a warning in console or handle logic, but we display raw math
// For UI purposes, we will just display the math but user should be careful.
}
// 7. Update DOM elements
document.getElementById("bmrCal").innerHTML = Math.round(bmr).toLocaleString();
document.getElementById("bmrKj").innerHTML = Math.round(bmrKj).toLocaleString();
document.getElementById("tdeeCal").innerHTML = Math.round(tdee).toLocaleString();
document.getElementById("tdeeKj").innerHTML = Math.round(tdeeKj).toLocaleString();
document.getElementById("lossCal").innerHTML = Math.round(lossCal).toLocaleString();
document.getElementById("lossKj").innerHTML = Math.round(lossKj).toLocaleString();
document.getElementById("gainCal").innerHTML = Math.round(gainCal).toLocaleString();
document.getElementById("gainKj").innerHTML = Math.round(gainKj).toLocaleString();
// 8. Show Result Box
document.getElementById("result").style.display = "block";
// Scroll to results on mobile
document.getElementById("result").scrollIntoView({ behavior: 'smooth', block: 'start' });
}