Who Should Use This Calculator?
Anyone aiming to maintain their current weight benefits from knowing their daily calorie needs. Athletes, fitness enthusiasts, and individuals managing their diet rely on this calculation to set a sustainable eating baseline. The tool works best for healthy adults with a body mass index (BMI) in the normal range.
The calculator uses the Mifflin-St Jeor equation, which research has shown to be more accurate than older methods for most populations. It accounts for resting metabolic functions—your body's energy use for breathing, circulation, and organ function—then multiplies that by your activity multiplier to reflect actual daily movement.
Calorie Maintenance Formula
The Mifflin-St Jeor equation calculates basal metabolic rate (BMR) differently for men and women, then applies an activity factor to estimate total daily energy expenditure:
BMR (women) = (10 × weight) + (6.25 × height) − (5 × age) − 161
BMR (men) = (10 × weight) + (6.25 × height) − (5 × age) + 5
Daily Calories = BMR × Activity Factor
weight— Body weight in kilogramsheight— Height in centimetresage— Age in yearsActivity Factor— Multiplier based on exercise frequency: sedentary (1.2), light activity 1–3 days/week (1.375), moderate 3–5 days/week (1.55), heavy 6–7 days/week (1.725), or very intense training (1.9)
How to Interpret Your Results
Your calculated maintenance calories represent the approximate energy intake needed to keep your current weight stable over time. This is your starting point, not a rigid prescription.
- To maintain weight: Eat at or near your calculated calorie level.
- To lose weight: Consume 300–500 calories below this number. Avoid dropping below your BMR, as extreme restriction impairs metabolism and nutrition.
- To gain muscle: Eat 300–500 calories above maintenance while prioritising strength training and adequate protein (1.6–2.2 g per kg of body weight).
Individual variation is significant—genetics, metabolic health, medications, and stress all influence actual calorie burn. Use this figure as a baseline and adjust based on real-world progress over 2–4 weeks.
Activity Level Multipliers Explained
Your activity factor is the second-most important variable after BMR. Sedentary office workers use a factor of 1.2, meaning daily calories equal roughly 20% more than resting needs. Someone exercising 6–7 days weekly uses 1.725, nearly doubling their BMR.
Be honest about your routine. Light activity means structured exercise just once or twice per week. Moderate means 3–5 sessions. Heavy means daily training or a physical job. Overestimating activity inflates your calorie allowance and can prevent weight loss; underestimating may lead to unnecessary hunger.
Common Pitfalls and Considerations
Avoid these mistakes when using your maintenance calorie estimate.
- Mistaking BMR for daily needs — Your basal metabolic rate alone is not enough. A person with a BMR of 1,500 kcal sitting all day still needs more. Always multiply BMR by your activity factor. Ignoring this step leads to massive underestimates.
- Overestimating activity level — Casual gym sessions once or twice weekly are not 'moderate' activity. Be conservative. A 20-minute walk counts as light activity, not moderate. Overestimating can add 200–400 unwanted calories to your daily budget.
- Ignoring natural variation — Your calorie burn fluctuates by 10–20% due to sleep, stress, hormones, and metabolism changes. This calculator gives an average, not an exact daily figure. Monitor weight trends over weeks, not days.
- Forgetting hidden calories in beverages — Tracking food intake accurately is harder than the maths suggests. Oils, sauces, drinks, and small snacks accumulate fast. Many people undercount by 10–20%, which compounds over months.