Introduction
This calorie calculator shows how many calories you need each day. It uses the Mifflin-St Jeor formula, the same method taught in NASM nutrition courses. You enter your age, sex, height, weight, and how active you are. Then you pick a goal: lose fat, maintain weight, or gain muscle.
You get three numbers back. Your BMR is the energy your body burns at rest. Your TDEE is what you burn in a full day, including movement and exercise. Your calorie target is the number to eat each day to reach your goal.
You also get a macro breakdown, so you know how many grams of protein, fat, and carbs to eat. A chart compares your target to common intakes. A food table shows how much of your day one apple, one egg, or one soda uses up. Set a goal weight and you will also see about how long it may take to get there.
You can switch between pounds and kilograms, or kcal and kilojoules, at any time. Nothing needs to be typed twice. Every step of the math is shown, so you can see exactly where your number comes from.
How to use our NASM Calorie Calculator
Enter your body details, activity level, and goal. The calculator shows your BMR, TDEE, daily calorie target, macro split, and how long it may take to reach your goal weight.
Unit System: Pick Imperial (lb, ft/in) or Metric (kg, cm). Your numbers change over for you, so you do not have to type them again.
Energy Unit: Choose kcal or kJ. All results, including the food table, use the unit you pick.
Age: Type your age in whole years, from 15 to 100. Age lowers the calorie need in the formula.
Biological Sex: Choose Male or Female. Each one uses a different constant in the Mifflin-St Jeor formula.
Height: Type your height and pick the unit. For ft + in, put feet in the first box and inches in the second box.
Current Weight: Type your weight now and pick lb, kg, or st. This sets both your BMR and your protein target.
Activity Level: Pick how much you move and train each week. This multiplier turns your BMR into your TDEE.
Primary Goal: Choose Lose Fat, Maintain Weight, or Gain Muscle. Lose Fat cuts 300–500 calories a day, Gain Muscle adds 250–500, and Maintain keeps your TDEE.
Goal Weight: Type the weight you want to reach. This is used only for the time-to-goal estimate.
Desired Rate of Change: Type how much weight you want to change each week. This is for reference, such as 1 lb (0.45 kg) per week.
Display macros as: Switch between grams per day and percent of calories to see your protein, fat, and carb split the way you like.
Calculate My Calories: Click it to jump to your full results. Use Reset to start over, or Print Results to save a copy.
Understanding Your Daily Calorie Needs
A calorie is a unit of energy. Your body uses calories to breathe, think, move, and heal. Food gives you calories back. When you eat about the same number of calories you burn, your weight stays the same. Eat fewer, and you lose weight. Eat more, and you gain weight.
BMR: What You Burn at Rest
BMR stands for Basal Metabolic Rate. It is the energy your body needs just to stay alive, even if you stayed in bed all day. Your heart, lungs, brain, and cells all use fuel. BMR is usually the biggest part of your daily calorie burn, often 60% to 70% of the total.
The most widely used way to estimate BMR is the Mifflin-St Jeor equation. It uses your weight, height, age, and biological sex. Bigger and younger bodies burn more at rest. As you age, your BMR slowly drops.
TDEE: What You Burn All Day
TDEE stands for Total Daily Energy Expenditure. This is your BMR plus everything else you do: walking, working, training, even fidgeting. To find it, your BMR is multiplied by an activity number between 1.2 and 1.9. The more you move, the higher the number. TDEE is your maintenance level. Eat that many calories and your weight should hold steady.
Deficits and Surpluses
To lose fat, most people eat 300 to 500 calories below their TDEE each day. That is a slow, steady pace that protects muscle and is easier to stick with. About 3,500 calories equals one pound of fat, so a 500-calorie daily deficit works out to roughly one pound a week.
To build muscle, eat 250 to 500 calories above your TDEE and lift weights. A small surplus adds muscle with less extra fat. Going much higher mostly just adds fat.
There is a floor to how low you should go. Men should not drop below 1,500 calories a day, and women below 1,200, without a doctor's help. Eating too little can cost you muscle, energy, and important vitamins and minerals.
Macronutrients: Where the Calories Come From
Calories come from three macronutrients:
- Protein (4 calories per gram). Builds and protects muscle. It also keeps you full longer. Active people often aim for 1.4 to 2.2 grams per kilogram of body weight.
- Fat (9 calories per gram). Needed for hormones and to absorb vitamins A, D, E, and K. About 25% to 35% of your calories is a common target.
- Carbohydrates (4 calories per gram). Your main fuel for hard training and daily energy. Carbs usually fill in whatever calories are left.
Why It Is an Estimate, Not a Rule
Every formula is a starting point. Real calorie needs change with genetics, sleep, stress, hormones, medicine, and how much you move without noticing. Two people the same size can differ by 200 to 300 calories a day. That is why a range works better than one exact number.
Use your target for two to three weeks. Track your weight and how you feel. If nothing changes and you want it to, adjust by about 100 to 200 calories a day and try again. Weigh yourself at the same time of day, since water, food, and salt can swing the scale by a few pounds overnight.
kcal vs. kJ
Food labels in the United States use "Calories," which really means kilocalories (kcal). Many other countries use kilojoules (kJ). One kcal equals 4.184 kJ. They measure the same energy, just on different scales.
Making the Number Work
Hitting a calorie goal is easier when you build meals around whole foods: lean protein, vegetables, fruit, whole grains, and healthy fats. These foods fill you up for fewer calories. Liquid calories from soda, juice, and alcohol add up fast and do not fill you up, so they are an easy place to cut. Slow, steady change beats a crash diet almost every time. The goal is a plan you can keep for months, not days.