Calorie Calculator

What this calorie calculator does

This calculator estimates the calories you need to maintain your current weight, then shows daily targets for gradual weight loss, moderate weight loss, fast weight loss, and corresponding weight gain. It uses a BMR formula and an activity multiplier to estimate total daily energy expenditure.

The targets are built from fixed daily deficits and surpluses: 250, 500, and 1,000 calories. A 500-calorie daily deficit is often described as roughly one pound of weight change per week, but actual results vary.

How to use this calculator

1. Choose US or metric units.
2. Enter age, sex, height, and weight.
3. Choose a BMR formula. Katch-McArdle also asks for body fat percentage.
4. Choose the activity level that matches a typical week.
5. Choose calories or kilojoules for the results.
6. Click Calculate to see maintenance calories and the target table.

The default example is a 25-year-old man who is 5 ft 10 in tall and weighs 165 lb, using Mifflin-St Jeor and a moderate activity level.

Calorie formulas

BMR = Mifflin-St Jeor, Revised Harris-Benedict, or Katch-McArdle
Maintenance calories = BMR × activity multiplier
Mild loss = maintenance − 250
Weight loss = maintenance − 500
Extreme loss = maintenance − 1,000
Mild gain = maintenance + 250
Weight gain = maintenance + 500
Fast gain = maintenance + 1,000

The percentages in the table show each target relative to maintenance. For example, 2,049 is 80% of a 2,549-calorie maintenance level.

What the results mean

• BMR: the resting energy estimate.
• Maintenance: estimated calories to keep weight stable at the selected activity level.
• Targets: daily calorie levels for the selected goal. A larger deficit or surplus is not automatically better; very aggressive targets can be difficult to sustain and may not be appropriate without medical supervision.

The default maintenance estimate is 2,549 Calories/day, with targets of 2,299, 2,049, 1,549, 2,799, 3,049, and 3,549 Calories/day.

Assumptions and limitations

The calculator uses a formula-based BMR estimate and a self-reported activity multiplier. It does not measure actual energy expenditure, food intake, or body composition. It does not account for medical conditions, medications, pregnancy, lactation, growth, or adaptive changes during long-term dieting.

A calorie target is not a meal plan. Food quality, protein intake, fiber, micronutrients, sleep, and resistance training all affect health and body composition. Very low calorie intake can be unsafe without medical supervision.

Frequently asked questions

How accurate is the maintenance estimate?

It is a starting point. Individual metabolism and activity vary. Track your weight and intake for two to three weeks and adjust based on the trend, not a single day.

Is a 1,000-calorie deficit safe?

Not for everyone. A 1,000-calorie daily deficit is aggressive and may be inappropriate for people with lower calorie needs or medical conditions. A smaller deficit is often easier to sustain.

Why are the targets fixed at 250, 500, and 1,000?

Those correspond to commonly used expectations of about 0.5, 1, and 2 pounds per week. The calculator shows the arithmetic; it does not guarantee that rate of change.

Does exercise change the result?

The activity multiplier accounts for a typical activity pattern. Adding a new exercise program can change both energy expenditure and appetite, so reassess after a few weeks.

Reference tables

Calorie targets

Activity level

Common foods

Meal plan examples

Calories burned in one hour

Food components

Calorie needs vary with age, sex, body size, activity, and health. These tables are planning references, not medical prescriptions.

Source

References:

• National Institute of Diabetes and Digestive and Kidney Diseases — Body Weight Planner
• Dietary Guidelines for Americans

Disclaimer

This calculator is for informational and educational purposes only. It is not medical advice or a personalized meal plan. Consult a registered dietitian or clinician before starting a weight-loss or weight-gain program.