Health calculators

Nasm Calorie Calculator

Updated Oct 7, 2026 By Infinity Calculator
Rate Formulas Sources Medical disclaimer
Units & Display
Unit System
Switching converts every value you have already entered — nothing needs re-typing.
1 kcal = 4.184 kJ. Calorie targets, BMR, TDEE and the food table all follow this choice.
Your Details
Whole years, 15–100.
Biological Sex
Mifflin-St Jeor uses a different constant for each (+5 / −161).
First box = feet, second box = inches.
Used for both BMR and your protein target.
Multiplier applied to BMR: ×1.55 (moderate exercise 3–5 days/week).
Your Goal
Primary Goal
Used only for the "time to goal" estimate.
Common choices: 0.5 lb (0.23 kg), 1 lb (0.45 kg) or 2 lb (0.91 kg) per week.
Live estimate
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Your Results

Daily Calorie Target — Lose Fat
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BMR — Basal Metabolic Rate
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Energy your body burns at complete rest (Mifflin-St Jeor).
TDEE — Total Daily Energy Expenditure
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BMR × activity multiplier, before any goal adjustment.
Realistic Accuracy Band
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±10% and ±20% around your target — adjust after 2–3 weeks of tracked results.
Estimated Time to Goal Weight
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Macronutrient Breakdown
Display macros as
Protein
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Preserves and builds lean muscle; most filling per calorie.
Fat
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Hormone production and absorption of vitamins A, D, E and K.
Carbohydrates
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Primary fuel for training intensity and daily energy.
Macro split for your calorie target.
Macro Grams / day Energy / day % of target
Your Target in Context

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Step-by-Step Solution
Common Foods vs. Your Target

Introduction

This calorie calculator shows how many calories you need each day. It uses the Mifflin-St Jeor formula, derived in 1990 from 498 healthy adults aged 19 to 78.1 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. Resting energy use is usually the biggest part of your daily calorie burn, about 60% of the total.2

A systematic review found the Mifflin-St Jeor equation the most reliable of the common ways to estimate resting calorie burn.3 It uses your weight, height, age, and biological sex. Bigger bodies burn more at rest. In the formula, each added year of age lowers the result by 5 calories.1

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

The Lose Fat goal sets your target 300 to 500 calories below your TDEE each day. The National Heart, Lung, and Blood Institute's guide puts a deficit of 500 to 1,000 calories a day at a loss of 1 to 2 pounds a week.4 The rule that about 3,500 calories equal one pound of body fat fits people with more than 30 kg of body fat and overstates the deficit leaner people need.5

The Gain Muscle goal sets your target 250 to 500 calories above your TDEE. Pair it with regular weight training.

The target never goes below 1,500 calories a day for men or 1,200 for women. Federal obesity guidance describes supervised low-calorie diets of 1,000 to 1,200 calories a day for most women and 1,200 to 1,600 for men.4 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).6 Builds and protects muscle. It also keeps you full longer. The International Society of Sports Nutrition puts the daily need of most exercising people at 1.4 to 2.0 grams per kilogram of body weight.7 This calculator uses 1.4 to 2.2 grams per kilogram for moderately to very active people and 1.0 to 1.2 for less active people.
  • Fat (9 calories per gram).6 Needed for hormones and to absorb vitamins A, D, E, and K. This calculator sets fat at 25% to 35% of your calories. For adults, the accepted range is 20% to 35% of calories from fat.13
  • Carbohydrates (4 calories per gram).6 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. 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.8 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.

Formulas used

Basal Metabolic Rate (Mifflin-St Jeor) 1
\mathrm{BMR} = 10m_{kg} + 6.25h_{cm} - 5a + s,\quad s = \begin{cases} +5 & \text{male} \\ -161 & \text{female} \end{cases}
Total Daily Energy Expenditure
\mathrm{TDEE} = \mathrm{BMR} \times A,\quad A \in \{1.2,\ 1.375,\ 1.55,\ 1.725,\ 1.9\}
Daily calorie target range (goal adjustment with safety floor)
\text{Target} = \max\!\left(\mathrm{TDEE} + \Delta,\ F\right),\quad \Delta \in \begin{cases} [-500,-300] & \text{lose} \\ 0 & \text{maintain} \\ [+250,+500] & \text{gain} \end{cases},\quad F = \begin{cases} 1500 & \text{male} \\ 1200 & \text{female} \end{cases}
Macronutrient targets (protein, fat, carbohydrate)
P = (1.0\text{--}1.2 \text{ or } 1.4\text{--}2.2)\, m_{kg},\quad F_g = \frac{(0.25\text{--}0.35)\,E_{mid}}{9},\quad C = \frac{E_{mid} - 4P - 9F_g}{4}
Time to goal weight from calorie-implied rate
r = \frac{|E_{target} - \mathrm{TDEE}| \times 7}{3500} \times 0.453592,\qquad t_{weeks} = \frac{|m_{kg} - m_{goal}|}{r},\qquad t_{months} = \frac{t_{weeks}}{4.345}
Accuracy band around target
E_{band} = E_{mid} \times (1 \pm 0.10),\qquad E_{wide} = E_{mid} \times (1 \pm 0.20)
Energy unit conversion
E_{kJ} = E_{kcal} \times 4.184
Food serving comparison
\%_{daily} = \frac{E_{food}}{E_{mid}} \times 100,\qquad N_{servings} = \frac{E_{mid}}{E_{food}}

Frequently asked questions

Which is more accurate, the Mifflin-St Jeor or the Harris-Benedict equation?

Mifflin-St Jeor is usually closer. A systematic review of the common equations found it the most reliable, predicting resting energy within 10% of measured in more people than any other.3 It was published in 1990.1 The Harris-Benedict equations date from 1918.9 In the Mifflin-St Jeor study, the Harris-Benedict equations overestimated measured resting energy by 5%.1

Both are still just estimates. Neither one knows your genes, sleep, or hormones.

Should I eat back the calories I burn during exercise?

Usually no. When you pick an activity level like moderate or very active, your training is already built into your daily number. Eating back workout calories on top of that counts them twice.

The one exception is a rare, very long session, like a 3-hour hike or long run. Then a small extra snack makes sense.

How much protein do I need to build muscle?

A review of the research points to at least 1.6 grams per kilogram of body weight a day, with 2.2 g/kg as the upper intake reported in the literature.10 That is roughly 0.7 to 1 gram per pound. For a 180 lb (82 kg) person that is about 130 to 180 grams a day.

Spread it across at least four meals of about 0.4 g/kg each.10

What happens if you eat below your BMR?

Short term, you lose weight fast. But a lot of that loss is muscle and water, not just fat. You may also feel tired, cold, hungry, and moody, and miss key vitamins and minerals.

The Lose Fat goal here keeps men at 1,500 calories a day or more and women at 1,200 or more, with a cut of 300 to 500 calories below your TDEE.

Why do men burn more calories than women?

Men usually carry more muscle and less fat at the same body weight. Muscle burns more energy at rest than fat does, so resting burn is higher.

The Mifflin-St Jeor formula shows this with a constant: it adds 5 for men and subtracts 161 for women.1 That works out to about a 166 calorie gap for two people of the same size and age.1

Can you lose fat and build muscle at the same time?

Yes, but mostly for beginners, people coming back from a break, or those with a lot of fat to lose. It is called body recomposition.

To do it, keep a small calorie cut, eat high protein, and lift weights several days a week. Progress on the scale will look slow, so track how clothes fit and how strong you are getting.

How long does it take to lose 10 pounds?

At 1 to 2 pounds a week, plan on 5 to 10 weeks. The National Heart, Lung, and Blood Institute's guide puts a deficit of 500 to 1,000 calories a day at a loss of 1 to 2 pounds a week.4

The first week often drops faster because of water weight. That is normal and not all fat.

Why has my weight loss stopped?

A stall almost always means calories in now match calories out. Common reasons:

  • You weigh less, so your body burns less than before.
  • Portions crept up, or bites and sips are not tracked.
  • You move less outside the gym without noticing.
  • Water from salt, stress, or a new workout hides fat loss.

Wait 2 to 3 weeks before you change anything. If the scale still has not moved, cut 100 to 200 calories or add daily steps.

How often should I recalculate my calorie needs?

Every time your weight changes by about 10 pounds (5 kg), or when your training or job changes a lot. A smaller body needs fewer calories, so an old number will stall your progress.

Also redo it if you switch goals, like moving from fat loss to muscle gain.

Does metabolism really slow down with age?

Less than most people think. In a large study of measured energy use, total and resting burn stayed steady from age 20 to 60, then declined.11

The bigger change is lost muscle and less movement over the years. Strength training and staying active keep your burn high far better than any supplement.

What counts as moderately active?

Moderate means real exercise 3 to 5 days a week, like 45 minutes of lifting, jogging, or a fitness class, plus normal daily walking.

Be honest here. Most people guess too high. If you sit at a desk all day and train 3 times a week, light to moderate is a better fit than very active.

Do calories from carbs, fat, and protein all count the same?

Not quite. Protein has 4 calories per gram, carbs 4, and fat 9.6 Digesting food uses energy too: about 20 to 30% of protein calories, 5 to 10% of carb calories and 0 to 3% of fat calories.12

Protein also keeps you full longer. That is why a high-protein diet makes a calorie cut feel easier.

Should I eat fewer calories on rest days?

You do not have to. Most people do better eating the same amount every day because it is simpler to follow and muscle repair happens on rest days too.

If you like the idea, shift some carbs from rest days to training days but keep the weekly total the same. Protein should stay high every day.

Sources

  1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241-247. doi:10.1093/ajcn/51.2.241. Accessed September 26, 2026.
  2. Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. International Journal of Obesity. 2010;34(Suppl 1):S47-S55. doi:10.1038/ijo.2010.184. Accessed September 26, 2026.
  3. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775-789. doi:10.1016/j.jada.2005.02.005. Accessed September 26, 2026.
  4. The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. National Heart, Lung, and Blood Institute. 2000;NIH Publication No. 00-4084. Accessed September 26, 2026.
  5. Hall KD. What is the required energy deficit per unit weight loss? International Journal of Obesity. 2008;32(3):573-576. doi:10.1038/sj.ijo.0803720. Accessed September 26, 2026.
  6. 21 CFR 101.9 — Nutrition labeling of food. Electronic Code of Federal Regulations (eCFR), U.S. Food and Drug Administration. 101.9(c)(1)(i). Accessed September 26, 2026.
  7. Jäger R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, et al. International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition. 2017;14:20. doi:10.1186/s12970-017-0177-8. Accessed September 26, 2026.
  8. NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity or field of science. National Institute of Standards and Technology. Accessed September 26, 2026.
  9. Harris JA, Benedict FG. A biometric study of human basal metabolism. Proceedings of the National Academy of Sciences of the United States of America. 1918;4(12):370-373. doi:10.1073/pnas.4.12.370. Accessed September 26, 2026.
  10. Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition. 2018;15:10. doi:10.1186/s12970-018-0215-1. Accessed September 26, 2026.
  11. Pontzer H, Yamada Y, Sagayama H, Ainslie PN, Andersen LF, Anderson LJ, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812. doi:10.1126/science.abe5017. Accessed September 26, 2026.
  12. Westerterp KR. Diet induced thermogenesis. Nutrition & Metabolism. 2004;1:5. doi:10.1186/1743-7075-1-5. Accessed September 26, 2026.
  13. Dietary Reference Intakes (DRIs): Acceptable Macronutrient Distribution Ranges. National Academies of Sciences, Engineering, and Medicine. Appendix J, Table J-5. Accessed October 7, 2026.

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