AtlasCalcsUtility Calculation Suite
September 2026 12 min read

Macro Calculator

Calculate your daily macronutrient targets — protein, carbs, and fat in grams — from your body metrics, activity level, and goal. Choose a proven preset or fine-tune a custom ratio, and get a per-meal breakdown.

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Age
years
Gender
Male Female
Height
cm
Weight
kg
Activity Level
Goal
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Macro Calculation Formulas

The Mifflin-St Jeor equation estimates BMR, which is scaled by an activity factor (TDEE) and a goal adjustment, then split into macro grams.

BMR = 10 × W(kg) + 6.25 × H(cm) − 5 × age + 5 (men) | − 161 (women)

Alternative Form

grams = daily kcal × macro% ÷ kcal-per-gram (P: 4, C: 4, F: 9)

Variables

SymbolNameUnitDescription
BMRBasal Metabolic Ratekcal/dayCalories burned at complete rest (Mifflin-St Jeor equation)
TDEETotal Daily Energy Expenditurekcal/dayBMR multiplied by an activity factor
CCalorie Targetkcal/dayTDEE plus or minus a goal adjustment (deficit or surplus)
P%, C%, F%Macro Split% of caloriesPercentages of total calories from protein, carbs, and fat
gGrams per daygMacro calories divided by energy density (4/4/9 kcal per gram)

Explanation

Mifflin-St Jeor (1990) is considered the most accurate BMR equation for the general population, outperforming the older Harris-Benedict and Katch-McArdle formulas when body composition is unknown. After the calorie target is set, each macro's share of calories is divided by its energy density to yield grams: 4 kcal/g for protein and carbohydrates, 9 kcal/g for fat.

Derivation

BMR × activity factor = TDEE. TDEE + goal adjustment = calorie target. Protein grams = (C × P%) / 4; Carb grams = (C × C%) / 4; Fat grams = (C × F%) / 9. Example: 2,000 kcal with 30% protein gives (2000 × 0.30)/4 = 150 g protein.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Estimate Basal Metabolic Rate (BMR) with the Mifflin-St Jeor equation.

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 (men) / − 161 (women)
Weight:80 kg
Height:178 cm
Age:30
Gender:Male
Intermediate: 10 × 80 + 6.25 × 178 − 5 × 30 + 5 = 800 + 1112.5 − 150 + 5
Result: BMR = 1,767.5 kcal/day
Step 2

Multiply BMR by the activity factor to get TDEE.

TDEE = BMR × activity multiplier
BMR:1,767.5 kcal
Activity:Moderate (1.55)
Intermediate: 1,767.5 × 1.55
Result: TDEE = 2,739.6 kcal/day
Step 3

Apply the goal adjustment to find the daily calorie target.

C = TDEE + goal adjustment
TDEE:2,739.6 kcal
Goal:Weight loss (−500 kcal)
Intermediate: 2,739.6 − 500
Result: C = 2,239.6 kcal/day
Step 4

Allocate calories to macros and convert to grams (balanced 30/40/30 split).

grams = C × split% ÷ kcal-per-gram
C:2,239.6 kcal
Protein:30% (4 kcal/g)
Carbs:40% (4 kcal/g)
Fat:30% (9 kcal/g)
Intermediate: Protein: 2239.6 × 0.30 ÷ 4 | Carbs: 2239.6 × 0.40 ÷ 4 | Fat: 2239.6 × 0.30 ÷ 9
Result: Protein ≈ 168 g | Carbs ≈ 224 g | Fat ≈ 75 g
Final Answer
~2,240 kcal/day → 168 g protein, 224 g carbs, 75 g fat

Worked Examples

See how the calculator works with different scenarios.

Scenario

A 30-year-old man, 178 cm, 80 kg, moderately active, aiming to lose about 1 lb per week with a balanced 30/40/30 split.

Inputs

Age:30
Gender:Male
Height:178 cm
Weight:80 kg
Activity:Moderate (1.55)
Goal:Weight loss (−500 kcal)
Split:30P / 40C / 30F

Calculation

BMR = 10×80 + 6.25×178 − 5×30 + 5 = 1,767.5. TDEE = 1,767.5 × 1.55 = 2,739.6. Target = 2,739.6 − 500 = 2,239.6 kcal.

Result

~2,240 kcal/day | Protein ≈ 168 g | Carbs ≈ 224 g | Fat ≈ 75 g

Interpretation

A 500 kcal daily deficit yields roughly 1 lb of fat loss per week (3,500 kcal ≈ 1 lb of fat). Protein at ~2.1 g/kg helps preserve muscle during the deficit.

What Are Macronutrients?

Macronutrients are the nutrients your body requires in gram quantities every day to produce energy: protein, carbohydrates, and fat. Alongside water, they form the bulk of the human diet, while micronutrients (vitamins and minerals) are needed in milligram amounts. Each macro plays a distinct role.

Protein — 4 kcal per gram

Protein supplies the amino acids used to build and repair muscle, organs, skin, hair, enzymes, hormones, and immune cells. Nine amino acids are essential, meaning they must come from the diet. Complete sources (meat, fish, eggs, dairy, soy) contain all nine; complementary plant pairings (rice and beans) can too. Protein also has the highest thermic effect of food (20-30% of its calories are burned in digestion) and is the most satiating macro, which is why higher-protein diets consistently perform well for fat loss.

Carbohydrates — 4 kcal per gram

Carbohydrates are the body's preferred fuel for high-intensity exercise and the primary energy source for the brain and central nervous system. They are stored as glycogen in muscle and the liver. Complex carbs (whole grains, legumes, vegetables, fruit) digest slowly and deliver fiber, while simple sugars digest quickly. Fiber, itself a carbohydrate, is essential for digestion, cholesterol management, and blood sugar control, with recommendations of 25-38 g daily.

Fat — 9 kcal per gram

Fat is the most energy-dense macro and is structurally essential: cell membranes, the sheaths around nerves, and hormones like testosterone and estrogen are all built from lipids. Fat also carries the fat-soluble vitamins A, D, E, and K. Unsaturated fats (olive oil, nuts, seeds, fatty fish) support cardiovascular health, while saturated and trans fats should be limited. Essential fatty acids (omega-3 and omega-6) cannot be made by the body and must come from food.

Popular Macro Splits by Goal

GoalProteinCarbsFatBest for
Balanced30%40%30%General health, maintenance
High protein40%30%30%Fat loss, muscle retention
Low carb35%20%45%Steady energy, appetite control
Keto25%5%70%Ketosis, fat-adapted diets
Endurance20%55-60%20-25%Runners, cyclists, team sports

Practical Tips

  • •Prioritize protein first: set 1.6-2.2 g per kg of body weight, then fill remaining calories with carbs and fat to suit your preference.
  • •Recalculate your macros every 4-6 weeks or after any 2-3 kg change in body weight — your TDEE moves with your weight.
  • •Pick a split you can sustain: the best macro ratio is the one you will actually follow for months, not the "optimal" one you abandon in a week.
  • •Weigh food with a scale for the first month. Volume estimates (cups, spoons) are commonly off by 20-40%.
  • •Keep fat at or above 0.5-1 g per kg: very low fat intake can disrupt hormone production, especially in women.
  • •Use flexible dieting (IIFYM): aim for 80% whole, nutrient-dense foods and 20% flexibility to keep the diet sustainable.
  • •Spread protein across 3-5 meals of 20-40 g each to support muscle protein synthesis throughout the day.
  • •On rest days, either keep macros constant (simplest) or drop 50-100 g of carbs while holding protein steady.
  • •Aim for 25-38 g of fiber per day — track it alongside your macros, since high-protein, low-carb splits can crowd out fiber.
  • •Adjust in small steps: if progress stalls for 2-3 weeks, change calories by 100-200 kcal rather than slashing them.

Common Mistakes

Treating macro percentages as grams
A 30/40/30 split means 30% of CALORIES from protein, not 30 grams. For a 2,500 kcal diet that is 187 g of protein, a very different amount. Always convert percentages through energy density: 4 kcal/g for protein and carbs, 9 kcal/g for fat.
Overestimating activity level
Most people with desk jobs are sedentary (1.2) or light (1.375), even with 2-3 gym sessions per week. Choosing "athlete" when you train 4 times per week can inflate TDEE by 400+ kcal and silently erase a deficit.
Using an outdated body weight
BMR scales with weight. If you have lost 5 kg since you first calculated your macros, your TDEE has dropped by roughly 50-80 kcal/day. Recalculate after every 2-3 kg change.
Copy-protein without checking absolutes
Percentage-based protein targets can become dangerously low (very high calorie diets) or absurdly high (very low calorie diets). Cross-check your protein percentage against 1.6-2.2 g/kg of body weight.
Forgetting alcohol calories
Alcohol supplies 7 kcal/g and is not a macro bucket in most trackers. Untracked drinks can add 300-700 kcal/day and stall fat loss even when macros are "on target".
Chasing daily perfection instead of weekly averages
Hitting macros within ±5-10 g per day is sufficient. Your body responds to weekly energy balance, not to whether Tuesday was exactly 168 g of protein.
Not counting cooking oils and sauces
A tablespoon of olive oil is 14 g of fat (126 kcal) and often invisible in "home cooking" entries. Log oils, butter, and dressings explicitly — they are frequently the hidden 200-400 kcal.
Setting an extreme deficit with high training volume
A 1,000 kcal deficit (2 lb/week) plus intense training is a recipe for muscle loss, fatigue, and injury. Larger deficits call for higher protein percentages and lower training volume.

Assumptions

This calculator makes the following assumptions to provide estimates:

Mifflin-St Jeor BMR: The calculator estimates BMR with the Mifflin-St Jeor equation, which is accurate within roughly ±10% for most adults.
Constant Activity Multiplier: The activity factor assumes a consistent weekly routine. Sporadic training weeks will shift your true TDEE up or down.
Steady 3,500 kcal per Pound Rule: Weekly weight-change rates assume approximately 3,500 kcal per pound of body fat; real-world water and glycogen shifts cause fluctuation.
Adults 18-80: Formulas are validated for adults. Growing teenagers, pregnant or breastfeeding women need different targets and should consult a professional.
No Medical Conditions: Thyroid disorders, PCOS, medications, and other conditions alter energy expenditure and are not modeled.

Limitations

Be aware of these limitations when using this calculator:

Estimate, Not a Measurement: TDEE estimates can be off by 200-400 kcal/day. Track actual weight trends for 2-3 weeks and adjust calories based on real-world results.
No Body Composition Input: Two people with identical height and weight but different body fat percentages have different energy needs. A body-fat-aware estimate would be more precise.
Not Medical or Dietetic Advice: This tool provides educational estimates only. Consult a registered dietitian or physician before starting any restrictive diet, especially with medical conditions.
No Micronutrient Planning: Only macronutrients are calculated. Vitamin, mineral, and fiber needs must be considered separately.

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Authoritative References

Information sources used in creating this calculator and educational content.

Macro & Nutrition Glossary

Technical terms used in mortgage calculations explained in plain language.

BMR (Basal Metabolic Rate)
The energy your body burns at complete rest to sustain vital functions like breathing, circulation, and cell repair. Typically 60-70% of total daily expenditure.
TDEE (Total Daily Energy Expenditure)
Your total daily calorie burn: BMR plus activity, exercise, and the thermic effect of food. Eating below TDEE causes weight loss; above it, weight gain.
Macronutrients (Macros)
The three nutrients consumed in gram quantities that provide energy: protein and carbohydrates (4 kcal/g) and fat (9 kcal/g).
Mifflin-St Jeor Equation
The BMR formula published in 1990, considered the most accurate general-population equation. It uses weight, height, age, and sex.
IIFYM (If It Fits Your Macros)
A flexible dieting approach in which any food is allowed as long as daily protein, carb, and fat targets are met.
Thermic Effect of Food (TEF)
Energy used to digest and absorb food. Protein has the highest TEF (20-30% of its calories), carbs 5-10%, fat 0-3%.
Net Carbs
Total carbohydrates minus fiber and sugar alcohols, used primarily in low-carb and keto dieting.
Ketosis
A metabolic state reached when carbohydrate intake is very low (typically under 20-50 g/day), causing the body to burn fat and produce ketones for fuel.
Calorie Deficit / Surplus
Eating fewer (deficit) or more (surplus) calories than your TDEE, driving fat loss or weight gain respectively.
Body Recomposition
Simultaneously losing fat and gaining muscle, typically achieved with a modest deficit, high protein, and resistance training.

Frequently Asked Questions

Answers to common questions about this calculator.

What are macronutrients (macros)?
Macronutrients are the nutrients your body needs in large amounts for energy: protein, carbohydrates, and fat. Protein and carbohydrates provide 4 calories per gram; fat provides 9. Protein builds and repairs tissue, carbs fuel high-intensity work and the brain, and fat supports hormones, vitamin absorption, and cell health. "Tracking macros" means monitoring how many daily grams of each you eat.
How does this macro calculator work?
It estimates your Basal Metabolic Rate with the Mifflin-St Jeor equation, multiplies by an activity factor to get your TDEE, applies a goal adjustment (a deficit for fat loss, a surplus for gain), then splits the resulting calories into protein, carb, and fat grams based on your chosen ratio using the 4/4/9 kcal per gram conversion.
What is the best macro ratio for weight loss?
There is no single best ratio, but research consistently supports higher protein during a deficit: roughly 30-40% protein, 30-40% carbs, and 20-30% fat is a common and effective starting point. Higher protein preserves lean mass and increases fullness. The best ratio is ultimately the one you can sustain while maintaining the calorie deficit.
What is the best macro ratio for muscle gain?
For muscle gain, aim for 25-35% protein (1.6-2.2 g/kg of body weight), 40-50% carbohydrates to fuel training, and 20-30% fat, with a 250-500 kcal surplus. The surplus provides energy for growth while the protein supplies the building blocks; excess protein beyond need does not add more muscle.
How many grams of protein per day do I need?
Sedentary adults need about 0.8 g per kg of body weight (the RDA). Active individuals benefit from 1.2-1.7 g/kg, and those building muscle or dieting hard benefit from 1.6-2.2 g/kg. For a 75 kg person this ranges from 60 g (sedentary) to 165 g (athlete).
How many carbs per day should I eat?
Dietary Guidelines recommend 45-65% of calories from carbs: 225-325 g on a 2,000 kcal diet. Endurance athletes may need 5-10 g/kg; keto dieters cap at 20-50 g. Carbs fuel high-intensity exercise and central nervous system function, so active people generally perform and feel better with moderate-to-high intakes.
How much fat per day is healthy?
Guidelines suggest 20-35% of calories from fat: 44-78 g on a 2,000 kcal diet. A practical floor is 0.5-1 g per kg of body weight to supply essential fatty acids and support hormone production. Very low fat intake (below 20%) can impair hormonal health, especially in women.
What is the difference between counting macros and counting calories?
Calories determine whether your weight goes up or down; macros determine the quality of that change. Two identical 2,000 kcal diets can produce very different results if one has 40% protein and the other 10%. Counting macros is essentially counting calories with composition control.
What is IIFYM (If It Fits Your Macros)?
IIFYM is a flexible dieting approach where no food is off-limits as long as your daily macro targets are met. It removes the "good food/bad food" rigidity of traditional diets, which improves adherence for many people. Best practice is to still build 80% of intake from nutrient-dense whole foods.
Does the macro split matter more than calories?
No. Total calories are the primary driver of weight change; the split influences body composition, performance, and satiety. A 500 kcal deficit produces fat loss whether the split is 30/40/30 or keto, but the higher-protein split will better preserve muscle and control hunger.
How do I adjust macros when weight loss stalls?
First verify tracking accuracy and re-weigh your food for a week. Then recalculate with your current body weight — a smaller body burns less. If still stalled, reduce calories by 100-200 (usually from carbs) or add 2,000-3,000 daily steps. Avoid slashing calories dramatically.
Should macros differ on rest days?
It is optional. Keeping macros identical every day is simpler and works well. The common refinement is trimming carbs on rest days (since glycogen demand is lower) while keeping protein and fat constant. Total weekly averages matter more than daily precision.
Is a keto macro split (70% fat) safe?
For most healthy adults, ketogenic diets are safe and effective for fat loss and can help with certain medical conditions, but they require diligence: electrolytes, fiber, and adequate protein (0.8-1.2 g/kg to prevent muscle loss). People with type 1 diabetes, pancreatitis, or liver disease should not attempt keto without medical supervision.
Can I build muscle while eating at a calorie deficit?
Yes, but it is limited. Beginners, those regaining muscle, and people with higher body fat can recomp: lift progressively, eat 1.8-2.4 g/kg protein, and keep the deficit moderate (250-500 kcal). Experienced lean trainees will gain muscle far more efficiently in a small surplus.
How often should I recalculate my macros?
Every 4-6 weeks, or whenever body weight changes by 2-3 kg (about 5 lb). Energy needs fall as you lose weight and rise as you gain. Also recalc if your activity level genuinely changes, e.g., you start or stop training for an event.
Do I need to hit my macros exactly?
No. Being within ±5-10 g per macro per day is effectively perfect, and weekly averages are what matter. If protein is 160 g ± 10 and fat is within 10 g, you will see the results you expect. Obsessive precision increases burnout risk without improving outcomes.
Does eating protein at night matter?
Total daily protein dominates outcomes. That said, distributing protein across 3-5 meals of 20-40 g (including a final protein-rich meal) appears to modestly favor muscle protein synthesis compared to a single skewed dose.
Are macro needs different for women?
Women generally have lower absolute calorie needs than men due to smaller average size and body composition, but percentage recommendations are similar. Some evidence suggests women, particularly athletes, benefit from slightly higher fat (25-35%) for hormonal and menstrual cycle health. Iron needs are higher for premenopausal women, reinforcing nutrient-dense food choices.
What is the thermic effect of food (TEF)?
TEF is the energy cost of digesting and absorbing what you eat. Protein burns 20-30% of its own calories in digestion, carbs 5-10%, fat 0-3%. This is why high-protein diets have a slight metabolic edge: a 200 g protein day burns 160-240 kcal in digestion alone.
Can this calculator be used for teens or children?
No. Mifflin-St Jeor and standard macro percentages are validated for adults 18 and older. Growing bodies have different protein, energy, and micronutrient requirements. Families should consult a pediatrician or registered dietitian for guidance.

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Page Information

Last Updated:

September 2026

Version:

2.0.0

License:

Free to use. Results are estimates for educational purposes only, not medical advice.