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Calorie Calculator

Find out how many calories you should eat per day for weight loss, maintenance, or muscle gain. Uses the Mifflin-St Jeor equation with activity-level adjustment.

How the Mifflin-St Jeor Equation Works

The Mifflin-St Jeor equation is considered one of the most accurate formulas for estimating resting metabolic rate (RMR). It calculates the number of calories your body needs at complete rest based on your weight, height, age, and sex. For men the formula is 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 5, and for women the constant changes to -161. Once you know your RMR, it is multiplied by an activity factor ranging from 1.2 for sedentary lifestyles to 1.9 for very active individuals. The result is your Total Daily Energy Expenditure, the number of calories you need to maintain your current weight.

Calorie Deficit vs. Surplus: Which Is Right for You?

A calorie deficit means eating fewer calories than your body burns, which forces it to use stored energy and leads to weight loss. A moderate deficit of 300 to 500 calories per day is generally recommended for sustainable fat loss without sacrificing muscle. On the other hand, a calorie surplus means eating more than you burn, which is necessary for building muscle mass. A surplus of 200 to 400 calories paired with resistance training supports lean muscle growth while minimising fat gain. Your choice depends on your goal: cut body fat, maintain your current physique, or build size and strength.

Frequently Asked Questions

How many calories should I eat to lose weight?▼
To lose weight, you need a calorie deficit. Most experts recommend reducing your maintenance calories by 300 to 500 per day, which typically results in 0.3 to 0.5 kg of fat loss per week. Crash diets with extreme deficits often backfire by slowing metabolism and increasing muscle loss.
Should I count calories every day?▼
Counting calories can be a helpful short-term learning tool to understand portion sizes and food composition. However, most people find long-term calorie counting unsustainable. A good approach is to track for a few weeks, build awareness, and then rely on mindful eating habits.
Does the type of calorie matter or just the total?▼
Both matter. While total calories determine weight change, the source of those calories affects satiety, muscle retention, energy levels, and overall health. A diet rich in protein, fibre, and whole foods performs better than one made up of processed foods, even at the same calorie count.

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