Daily Calorie Intake Calculator

The calculator processes six core inputs:

• Gender
• Age
• Weight (kg)
• Height (cm)
• Activity Level
• Goal

From these values, it produces three outputs:

• Basal Metabolic Rate (BMR)
• Maintenance Calories
• Recommended Daily Intake

The calculation follows a logical metabolic progression: first determining resting energy needs, then adjusting for lifestyle activity, and finally adapting the result according to the selected objective.

1. Basal Metabolic Rate (BMR)

Basal Metabolic Rate is the amount of energy the body uses while completely at rest.

This includes:

• Breathing
• Blood circulation
• Cell regeneration
• Brain activity
• Temperature regulation
• Organ function

BMR represents the minimum calories needed to stay alive.

A larger body requires more energy, while age generally reduces metabolic demand due to natural muscle loss and hormonal adaptation.

The calculator estimates BMR using the Mifflin–St Jeor metabolic equation.

For Men

For Women

Where:

• W = weight in kilograms
• H = height in centimeters
• A = age in years

The diagram shows how body size and age combine to estimate resting calorie demand.

2. Maintenance Calories

Maintenance calories represent total daily energy expenditure after accounting for movement and exercise.

The calculator multiplies BMR by an activity factor.

Activity factors:

Higher movement means greater energy expenditure.

As physical activity increases, calorie requirements rise proportionally.

3. Recommended Daily Intake

The calculator adjusts maintenance calories according to the selected goal.

Maintain Weight

Lose Weight

A calorie deficit promotes fat loss.

This usually supports gradual weekly weight reduction.

Gain Weight

A calorie surplus supports tissue growth.

This supports steady mass increase when combined with resistance training.

Worked Exercise

Input Data

• Gender: Male
• Age: 24
• Weight: 78 kg
• Height: 180 cm
• Activity Level: Moderately Active
• Goal: Lose Weight

Step 1: Calculate BMR

Step 2: Maintenance Calories

Step 3: Fat-Loss Intake

Results

Basal Metabolic Rate: 1790 kcal/day Maintenance Calories: 2775 kcal/day Recommended Intake: 2275 kcal/day

Interpretation

This result means:

• The body burns 1790 calories at complete rest
• Daily lifestyle raises total use to 2775 calories
• Eating 2275 calories daily creates a controlled deficit

If sustained consistently, this supports gradual fat loss while preserving muscle when paired with adequate protein intake and exercise.

Practical Training Exercise

Repeat the process with these values:

• Female
• 30 years
• 65 kg
• 168 cm
• Lightly Active
• Gain Weight

Calculate:

1. BMR
2. Maintenance calories
3. Final recommended intake

This exercise strengthens understanding of how body composition, movement, and goals combine to define calorie needs.