No upload, 100% local, no account

Calorie Calculator

Estimate your daily calorie needs from your BMR and activity level.

How Calorie Calculator works

The Calorie Calculator uses the Mifflin-St Jeor equation, the formula most widely recommended by registered dietitians since a 2005 comparative study found it the most accurate predictor of resting metabolic rate, to calculate your Basal Metabolic Rate (BMR). Your BMR is then multiplied by an activity factor to derive your Total Daily Energy Expenditure (TDEE), the total calories your body needs to maintain your current weight. The whole calculation runs locally in your browser: your age, height, weight and activity level are never sent to a server.

From your TDEE, the tool derives three daily calorie targets: a 500 kcal deficit for gradual fat loss (roughly 0.45 kg or one pound per week by the 3500 kcal rule), your maintenance level, and a 500 kcal surplus for gradual lean mass gain. Metabolism varies significantly between individuals; the figures are informational estimates, not medical advice.

Written by Bastien Sulyan

How to use Calorie Calculator, step by step

  1. Select your biological sex (the formula has different constants for men and women).
  2. Enter your age in years.
  3. Enter your height in centimetres or feet and inches.
  4. Enter your weight in kilograms or pounds.
  5. Select your activity level from the five preset options (sedentary to extra active).
  6. Read your BMR, TDEE and the three calorie targets from the result panel.

Common use cases

  • Getting a calorie baseline before starting a structured diet to know the maintenance level to adjust from.
  • Checking whether a prescribed daily calorie goal from a fitness app sits within a reasonable range of your calculated TDEE.
  • Explaining to a client or student the difference between BMR and TDEE and why the activity multiplier matters.
  • Estimating how many calories to add back on training days versus rest days when following a calorie-cycling protocol.

Frequently asked questions

Does this calculator upload my data anywhere?

No. Every calculation runs in your browser. Your age, weight, height and sex are never sent to any server. The arithmetic is plain JavaScript and the tool works offline once the page has loaded.

What is the Mifflin-St Jeor formula?

For men: BMR = (10 times weight in kg) + (6.25 times height in cm) minus (5 times age in years) + 5. For women: BMR = (10 times weight in kg) + (6.25 times height in cm) minus (5 times age in years) minus 161. Example for a 35-year-old man, 80 kg, 180 cm: BMR = 800 + 1125 minus 175 + 5 = 1755 kcal per day.

What are the activity level multipliers?

TDEE = BMR times the activity factor: Sedentary (little or no exercise) = 1.2; Lightly active (1 to 3 days per week) = 1.375; Moderately active (3 to 5 days per week) = 1.55; Very active (6 to 7 days per week) = 1.725; Extra active (physical job plus daily exercise) = 1.9. Most desk-job workers with occasional gym visits fall in the lightly to moderately active range.

Is the 500 kcal deficit rule accurate?

The rule approximates 0.45 kg (one pound) of fat loss per week because one pound of body fat stores roughly 3500 kcal. In practice, metabolic adaptation, water retention and muscle mass changes mean actual results vary from person to person. Use the figure as a starting estimate and adjust based on observed progress over two to four weeks.

Are these calorie numbers medical advice?

No. The numbers are estimates for general informational purposes. Individual metabolic rates, health conditions, medications and lifestyle factors all affect how your body responds to calorie changes. Always consult a registered dietitian or physician before making significant changes to your diet.

How does this differ from the Harris-Benedict formula?

The original Harris-Benedict equation (1919) and its revised 1984 version tend to overestimate BMR by 5 to 15 percent compared to indirect calorimetry. The Mifflin-St Jeor formula (1990) was validated against a broader, more modern population and is now preferred by most clinical dietetics guidelines.

Related tools

Keep everything local, explore complementary tools.

All calculators