Calorie Calculator
This calculator works out how many calories you need each day to maintain, lose or gain weight, using the Mifflin-St Jeor equation recommended by the Academy of Nutrition and Dietetics. Enter your sex, age, height and weight, choose your activity level from sedentary to extra active, and pick a goal from losing weight fast to gaining weight. It first works out your Basal Metabolic Rate (BMR), the calories your body burns at rest, then multiplies this by your activity level to give your Total Daily Energy Expenditure (TDEE), the calories you burn including everyday movement and exercise. Your results show your BMR, your maintenance calories, a daily calorie target adjusted for your chosen goal, and the estimated weekly weight change that target should produce. Below this you get a breakdown of calorie targets for every goal, plus an estimated macronutrient split of protein, carbohydrates and fat in grams for a balanced diet. Use it to set a realistic daily target before planning meals or a training programme, and be honest about your activity level, as overestimating it is a common reason people fail to lose weight. These are population-level estimates only, not medical advice, so check with a doctor or registered dietitian before making major changes to your diet.
1. Your Details
2. Activity Level
Calorie Targets
Macro Estimates (Balanced)
How Calories Are Calculated
This calculator uses the Mifflin-St Jeor equation (1990), which is considered the most accurate formula for estimating Basal Metabolic Rate (BMR) by the Academy of Nutrition and Dietetics. Your BMR is the number of calories your body burns at rest to maintain basic functions like breathing, circulation, and cell production. Your Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor.
The Mifflin-St Jeor Equation
Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
Activity Level Multipliers
| Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1-3 days/week | 1.375 |
| Moderately active | Moderate exercise 3-5 days/week | 1.55 |
| Very active | Hard exercise 6-7 days/week | 1.725 |
| Extra active | Very hard exercise, physical job | 1.9 |
Weight Loss and Gain Guidelines
One kilogram of body fat contains approximately 7,700 calories. A daily deficit of 500 calories results in approximately 0.5 kg of weight loss per week (500 x 7 = 3,500 cal = ~0.45 kg). It is generally recommended not to eat below 1,200 calories per day (women) or 1,500 (men) without medical supervision, as this can lead to nutrient deficiencies and metabolic slowdown.
Who this calculator is for
This calculator is for anyone estimating their daily energy needs in New Zealand, whether the goal is losing, maintaining or gaining weight, and for people planning meals or a training programme around a calorie target.
What this calculator assumes
- The age, height, weight, sex and activity level you enter.
- A standard BMR formula (such as Mifflin-St Jeor) scaled by activity.
- Estimates are general; real needs vary with metabolism, health and muscle mass.
- This is general information, not medical or dietary advice.
Related Calculators
- TDEE Calculator (detailed)
- Calorie Deficit Calculator
- Basal Metabolic Rate (BMR) Calculator
- BMI Calculator
Sources: Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990. Academy of Nutrition and Dietetics evidence analysis library.
This calculator provides estimates based on the Mifflin-St Jeor equation and population-level activity multipliers. Individual calorie needs vary based on genetics, body composition, metabolism, and other factors. Consult a registered dietitian or doctor before making significant changes to your diet, especially if you have a medical condition.