About Macronutrient Calculator
We built this free, science-backed macro calculator so anyone can get personalized protein, carb, and fat targets without signing up, paying, or handing over personal data.
What This Calculator Does
Our free macronutrient calculator helps you determine exactly how many grams of protein, carbohydrates, and fat you should eat daily based on your body, activity level, and specific goals.
The calculator includes four specialized tools:
- Daily Macros Calculator — Calculate your baseline macronutrient needs for maintaining, losing, or gaining weight
- Weight Loss Macros — Optimized macro splits with higher protein to preserve muscle during a caloric deficit
- Muscle Gain Macros — Calculate your caloric surplus and macro distribution for building lean muscle
- Keto Macro Calculator — Specialized calculator for ketogenic diets with customizable carb limits
Ready to try it? Open the Macro Calculator and get your numbers in under 30 seconds.
Our Methodology
We use the Mifflin-St Jeor equation to calculate your Basal Metabolic Rate (BMR). Published in 1990, it has been validated in dozens of subsequent studies and is recommended by the Academy of Nutrition and Dietetics as the most accurate predictive equation for most healthy adults.
For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
Your BMR is then multiplied by an activity factor to determine your Total Daily Energy Expenditure (TDEE):
- Sedentary (desk job): BMR x 1.2
- Lightly active (1-2 days/week): BMR x 1.375
- Moderately active (3-5 days/week): BMR x 1.55
- Very active (6-7 days/week): BMR x 1.725
- Extremely active (athlete): BMR x 1.9
How Mifflin-St Jeor Compares to Other Equations
Three BMR equations dominate the nutrition science literature. Here is how they differ:
Harris-Benedict (1919, revised 1984) — The oldest widely used equation. It tends to overestimate caloric needs by 5-15%, particularly in overweight individuals, because it was derived from a small sample of mostly lean subjects. Many online calculators still default to Harris-Benedict, which can stall weight-loss progress.
Katch-McArdle (1996) — Uses lean body mass (LBM) instead of total weight, making it potentially more accurate for very lean or very muscular individuals. The downside: it requires a body-fat percentage measurement, which most people do not have. If your body-fat estimate is off, the result can be less accurate than Mifflin-St Jeor.
Mifflin-St Jeor (1990) — Strikes the best balance between accuracy and accessibility. A 2005 systematic review in the Journal of the American Dietetic Association concluded that Mifflin-St Jeor predicted resting metabolic rate within 10% of measured values more often than any other equation tested. That is why we chose it.
Macronutrient distribution is then calculated based on your goal, using evidence-based ratios supported by sports nutrition research from the Examine.com protein intake guide and the International Society of Sports Nutrition (ISSN).
How We Compare
There are many nutrition tools online. Here is an honest comparison of ours against the most popular alternatives:
| Feature | This Calculator | MyFitnessPal | NIDDK Body Weight Planner | Calculator.net |
|---|---|---|---|---|
| Price | 100% free | Free (basic) / $20/mo premium | 100% free | 100% free |
| Account required | No | Yes | No | No |
| BMR formula | Mifflin-St Jeor | Mifflin-St Jeor (premium) | NIH research model | Mifflin-St Jeor |
| Keto mode | Yes (20/30/50g) | Manual only | No | No |
| Goal-specific macros | 4 modes | Custom only | Calories only | 1 mode |
| Privacy | No data stored | Data collected | No data stored | Ads / trackers |
| Mobile-friendly | Yes | App-based | Partial | Yes |
| Ad-free | Yes | No (free tier) | Yes | No |
The NIDDK Body Weight Planner is excellent for long-term weight projections, but it does not provide macro breakdowns. MyFitnessPal is great for daily food logging, but its macro goals are locked behind premium. Our calculator fills the gap: fast, free macro targets you can then track in any app you prefer.
Who This Calculator Is For
This calculator is designed for:
- People wanting to lose weight — Get a sustainable caloric deficit with high protein to preserve muscle
- Fitness enthusiasts — Optimize nutrition for gym performance and body composition
- Bodybuilders — Calculate precise macros for cutting or bulking phases
- Keto dieters — Determine the right fat, protein, and carb limits for ketosis
- Anyone tracking macros — Get personalized starting numbers instead of generic recommendations
For more detail, read our Counting Macros for Beginners guide.
The Team Behind This Calculator
Macronutrient Calculator is a small, independent project built by a team that cares about evidence-based nutrition and user-friendly design.
Our backgrounds span web development, data science, and nutrition coaching. We are not a venture-backed startup, and we do not sell supplements or meal plans. This site exists to provide a single thing well: accurate, free macro calculations.
Every formula, activity multiplier, and macro ratio used on this site is sourced from peer-reviewed research. We review the literature regularly and update our methodology when better evidence emerges. If you spot an error or have a suggestion, please reach out via our contact page.
Limitations & Disclaimer
While our calculator uses scientifically-validated formulas, please understand that:
- These are estimates — individual metabolism varies by 10-15%
- Results should be used as a starting point, then adjusted based on real-world progress
- This is not medical advice — consult a healthcare provider for personalized nutrition guidance
- People with medical conditions, eating disorders, or who are pregnant/nursing should seek professional guidance
Use these numbers for 2-3 weeks, track your results, then adjust as needed. No calculator can account for your unique metabolism. Read our Macro Myths Debunked article for common misconceptions.
Why We Built This
We created this calculator because most macro calculators online are either too simplistic, locked behind paywalls, or require you to create an account.
Our calculator is:
- 100% free — No accounts, no premium features, no paywalls
- Privacy-focused — All calculations happen in your browser; we don't store your data
- No ads interrupting your experience — Clean, focused interface
- Mobile-friendly — Works on any device
- Based on science — Using validated formulas, not arbitrary numbers
The Science Behind Our Calculator
Every result our calculator produces follows a three-step scientific process: estimate your Basal Metabolic Rate (BMR), scale it to your Total Daily Energy Expenditure (TDEE), then distribute those calories across protein, carbohydrates, and fat based on your goal. Below we walk through each step with a fully worked example so you can verify the math yourself.
Step 1: Calculate BMR Using Mifflin-St Jeor
The Mifflin-St Jeor equation was published in 1990 in the American Journal of Clinical Nutrition and has since become the gold standard for predicting resting energy expenditure. It uses four inputs: weight (kg), height (cm), age (years), and biological sex.
For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
- Weight: 180 lbs = 81.6 kg
- Height: 5'10" = 177.8 cm
- Age: 30 years
- BMR = (10 x 81.6) + (6.25 x 177.8) - (5 x 30) + 5
- BMR = 816 + 1,111.25 - 150 + 5 = 1,782 calories/day
- Weight: 140 lbs = 63.5 kg
- Height: 5'5" = 165.1 cm
- Age: 28 years
- BMR = (10 x 63.5) + (6.25 x 165.1) - (5 x 28) - 161
- BMR = 635 + 1,031.9 - 140 - 161 = 1,366 calories/day
Step 2: Multiply BMR by Activity Factor to Get TDEE
Your TDEE accounts for all the calories you burn beyond your basal rate, including exercise, walking, fidgeting (known as NEAT), and the thermic effect of food. We use the Katch-McArdle activity multipliers originally adapted from work by Harris and Benedict:
| Activity Level | Multiplier | Description | Example (BMR 1,782) |
|---|---|---|---|
| Sedentary | 1.2 | Desk job, minimal walking | 2,138 cal/day |
| Lightly active | 1.375 | Light exercise 1-2 days/week | 2,450 cal/day |
| Moderately active | 1.55 | Moderate exercise 3-5 days/week | 2,762 cal/day |
| Very active | 1.725 | Hard exercise 6-7 days/week | 3,074 cal/day |
| Extremely active | 1.9 | Professional athlete / physical job + training | 3,386 cal/day |
Continuing our example: a moderately active 30-year-old male with a BMR of 1,782 would have a TDEE of 1,782 x 1.55 = 2,762 calories/day.
Step 3: Distribute Calories Across Macronutrients
Once you have your TDEE, the final step is splitting those calories into protein, carbohydrates, and fat. The split depends on your goal. Here is how we calculate it for a weight-loss goal using the 40/30/30 split at a 500-calorie deficit:
- Target calories: 2,762 - 500 = 2,262 cal/day
- Protein (40%): 2,262 x 0.40 = 905 cal / 4 cal per gram = 226g protein
- Carbs (30%): 2,262 x 0.30 = 679 cal / 4 cal per gram = 170g carbs
- Fat (30%): 2,262 x 0.30 = 679 cal / 9 cal per gram = 75g fat
For more worked examples across different goals, see our How to Calculate Macros guide and our Calorie and Macro Calculator walkthrough.
Nutrition Science Fundamentals
Understanding macronutrients at a deeper level helps you make informed decisions about your diet. Here is a comprehensive overview of the three macronutrients, plus the often-overlooked role of micronutrients and energy balance.
Protein: The Building Block
Protein is composed of 20 amino acids, 9 of which are essential (your body cannot synthesize them). It plays a critical role in muscle protein synthesis (MPS), immune function, enzyme production, and satiety signaling. According to the World Health Organization, the minimum safe intake is 0.83 g/kg/day, but active individuals benefit from significantly more. A 2018 meta-analysis by Morton et al. found that protein intakes up to 1.6 g/kg/day maximized resistance-training-induced muscle gains. For practical guidance, see our Protein Intake Guide.
Protein also has the highest thermic effect of food (TEF) at 20-30%, meaning your body burns 20-30% of protein calories just digesting it. This is one reason why high-protein diets produce superior fat loss results even at similar calorie levels.
Carbohydrates: The Fuel Source
Carbohydrates are your body's preferred energy source during moderate-to-high-intensity exercise. They are stored as glycogen in muscles (approximately 400g) and the liver (approximately 100g). When glycogen stores are depleted, performance drops rapidly. The American College of Sports Medicine (ACSM) recommends 3-12 g/kg/day depending on exercise volume and intensity. Our Carb Calculator Guide helps you pinpoint your ideal intake.
Carbohydrates are classified as simple (sugars) or complex (starches and fiber). Fiber, a non-digestible carbohydrate, is critical for gut health, cholesterol regulation, and blood sugar control. The Harvard Nutrition Source recommends 25-30g of fiber daily from whole food sources.
Fat: The Hormone Regulator
Dietary fat is essential for the production of steroid hormones (testosterone, estrogen, cortisol), cell membrane integrity, and the absorption of fat-soluble vitamins A, D, E, and K. Research shows that chronic fat intakes below 20% of total calories can impair hormonal function, particularly testosterone in men. The National Heart, Lung, and Blood Institute recommends 20-35% of calories from fat. Learn more in our Fat Calculator Guide.
Micronutrients and Energy Balance
While macronutrients provide calories, micronutrients (vitamins and minerals) are needed in small amounts for metabolic processes, bone health, immune function, and hundreds of enzymatic reactions. A diet that hits your macro targets but consists entirely of processed food may lack essential micronutrients. This is why we recommend building your diet around whole foods first, then filling gaps with flexible choices. The NIH Office of Dietary Supplements maintains comprehensive fact sheets on every essential vitamin and mineral.
Energy balance is the fundamental principle underlying all weight change. When energy intake (calories consumed) exceeds energy expenditure (calories burned), the excess is stored as body fat. When expenditure exceeds intake, stored energy is mobilized. This principle is governed by the first law of thermodynamics and is the foundation of every diet strategy, from keto to flexible dieting.
Evidence-Based Approach
Unlike many online calculators that use arbitrary percentages or outdated formulas, every number our calculator produces is traceable to published, peer-reviewed research. Here is our methodology for staying evidence-based:
- Primary sources only: We derive our formulas from studies published in journals indexed on PubMed and the Journal of the International Society of Sports Nutrition
- Systematic reviews preferred: When available, we use conclusions from meta-analyses and systematic reviews rather than individual studies, reducing the risk of cherry-picking
- Regular updates: We review the sports nutrition literature quarterly and update our methodology when new high-quality evidence warrants a change
- Transparent formulas: Every equation used is displayed on this page so users and professionals can verify our calculations independently
- Conservative estimates: When evidence is inconclusive, we default to the more conservative (safer) recommendation, consistent with guidelines from the Academy of Nutrition and Dietetics
Our approach aligns with the ISSN Position Stands on protein, carbohydrate, fat, and energy needs for active individuals. For the general population, we also reference the Dietary Guidelines for Americans 2020-2025 and WHO Healthy Diet guidelines.
Our Calculation Methodology: Step-by-Step Breakdown
The following table summarizes every step in our calculation pipeline, from raw input to final macro gram targets. This transparency allows registered dietitians, personal trainers, and researchers to verify our approach.
| Step | What Happens | Formula / Source | Output |
|---|---|---|---|
| 1. Unit Conversion | Convert lbs to kg, feet/inches to cm | weight(kg) = lbs / 2.205; height(cm) = inches x 2.54 | Metric values |
| 2. BMR Estimation | Calculate basal metabolic rate | Mifflin-St Jeor (1990) — PubMed | Calories/day at rest |
| 3. TDEE Calculation | Multiply BMR by activity factor | Activity multipliers 1.2 to 1.9 | Total daily energy expenditure |
| 4. Goal Adjustment | Apply caloric surplus or deficit | Loss: -500 cal; Gain: +300-500 cal; Maintain: 0 | Target daily calories |
| 5. Protein Target | Set protein grams based on goal and bodyweight | 0.7-1.2 g/lb — Morton 2018 | Grams of protein |
| 6. Fat Target | Set fat as percentage of remaining calories | 20-35% of calories — DGA | Grams of fat |
| 7. Carb Target | Fill remaining calories with carbohydrates | Remaining cal / 4 cal per gram | Grams of carbs |
For keto mode, steps 5-7 are modified: carbohydrates are capped at 20-50g/day, protein is set at a moderate level (0.6-0.8 g/lb), and fat fills the remaining calories. Learn more in our Keto Macro Calculator Guide.
How We Compare: Extended Feature Matrix
We regularly evaluate our calculator against the most popular tools available. Below is an extended comparison covering 12 key features across 6 popular calculators and tools.
| Feature | MacronutrientCalculator.org | MyFitnessPal | Cronometer | MacroFactor | Calculator.net | NIDDK BWP |
|---|---|---|---|---|---|---|
| Price | Free | Free / $20/mo | Free / $50/yr | $12/mo | Free | Free |
| Account required | No | Yes | Yes | Yes | No | No |
| BMR formula | Mifflin-St Jeor | Mifflin-St Jeor | Mifflin-St Jeor | Adaptive algorithm | Mifflin-St Jeor | NIH model |
| Keto mode | Yes | Manual | Yes | Yes | No | No |
| Goal-specific splits | 4 modes | Custom | Custom | AI-adjusted | 1 mode | Calories only |
| Food logging | No | Yes | Yes | Yes | No | No |
| Barcode scanning | No | Yes | Yes | Yes | No | No |
| Micronutrient tracking | No | Limited | Yes (82+) | Limited | No | No |
| Privacy (no data stored) | Yes | No | No | No | No (ads) | Yes |
| Ad-free | Yes | No (free) | Yes | Yes | No | Yes |
| Mobile-friendly | Yes | App | App | App | Yes | Partial |
| Speed to results | < 30 seconds | 5+ minutes | 3+ minutes | 2+ minutes | 1 minute | 2 minutes |
Our calculator is designed to complement tracking apps rather than replace them. Get your macro targets here in seconds, then enter them into your preferred tracking app for daily food logging.
Explore Our Guides
We have published over 30 in-depth guides covering every aspect of macronutrient nutrition. Here are some of the most popular, organized by topic:
Getting Started
- How to Calculate Macros — Complete beginner's walkthrough of the calculation process
- Counting Macros for Beginners — Day-one guide to starting macro tracking
- Free Macro Calculator Guide — How to use our tool and interpret results
- Macro Ratio Explained — Understanding what 40/30/30 means and why it matters
Goal-Specific Guides
- Macros for Weight Loss — Optimal deficit and macro ratios for fat loss
- Macros for Muscle Gain — Surplus calculations for lean bulking
- Cutting Diet Macros — Competition-level cutting strategies
- Bulking Diet Macros — Clean vs. dirty bulk approaches
- Maintenance Macros Guide — Holding your current weight
- Reverse Dieting Explained — Gradually increasing calories post-diet
Diet Types & Special Populations
- Keto Macro Calculator — Ketogenic diet macro setup
- IIFYM Calculator Guide — Flexible dieting explained
- Macro Calculator for Women — Female-specific considerations
- Macro Calculator for Athletes — Performance-focused nutrition
- Macro Calculator for Seniors — Age-appropriate nutrition
- Vegan Macro Calculator — Plant-based macro planning
- Vegetarian Macro Guide — Lacto-ovo vegetarian approach
Frequently Asked Questions
We use the Mifflin-St Jeor equation, which the Journal of the American Dietetic Association identified as the most accurate BMR prediction method in a 2005 systematic review. Every macro ratio is derived from peer-reviewed sports nutrition research, not made-up percentages.
No. All calculations happen entirely in your browser using JavaScript. Your weight, height, age, and results are never sent to our server. We do not use analytics cookies or third-party trackers.
Recalculate every time your weight changes by 10-15 pounds, or whenever your activity level changes significantly. At a minimum, revisit your numbers every 6-8 weeks. For a deeper explanation, see our Maintenance Macros Guide.
Mifflin-St Jeor is more accurate than Harris-Benedict for overweight and obese individuals, but all predictive equations lose accuracy at extreme body weights. If your BMI is above 40, consider getting indirect calorimetry through a dietitian for a measured RMR. Our numbers are still a solid starting point.
We strongly recommend working with a registered dietitian during pregnancy and lactation. Caloric and protein needs increase significantly (roughly 300-500 extra calories per day), and standard formulas do not account for fetal development or milk production.
Any app that lets you set custom macro targets will work. Popular options include MyFitnessPal, Cronometer, MacroFactor, and Lose It. Calculate your macros here, then enter those targets into your preferred app. Our Tracking Apps Guide reviews the best options.
On a ketogenic diet, excessive protein can be converted to glucose through gluconeogenesis, potentially disrupting ketosis. Our keto calculator uses a moderate protein target (around 0.6-0.8g per pound of body weight) to keep you in ketosis while preserving muscle. For details, see our Keto Macro Calculator Guide.
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain basic life functions like breathing, circulation, and cell production. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for exercise, walking, and daily movement. TDEE is always higher than BMR. Your macro targets should be based on TDEE, not BMR. For a deep dive, read our TDEE Calculator Guide.
Yes. The BMR and TDEE calculations are diet-agnostic since they are based on your body composition and activity level, not what you eat. The macro gram targets we provide work for any dietary pattern. The key challenge for plant-based dieters is reaching protein targets from incomplete amino acid sources. Our Vegan Macro Calculator and Vegetarian Macro Guide address food selection strategies specifically for plant-based eaters.
For weight loss, we apply a 500-calorie deficit from your TDEE and increase the protein ratio to 40% of calories (or approximately 1.0-1.2 g/lb of bodyweight) to preserve lean muscle tissue. For muscle gain, we add a 300-500 calorie surplus and shift more calories toward carbohydrates (45%) to fuel intense training, while keeping protein at 30% of calories (approximately 0.8-1.0 g/lb). Learn the details in our Weight Loss Macros and Muscle Gain Macros guides.
Different calculators use different BMR equations (Harris-Benedict, Mifflin-St Jeor, Katch-McArdle), different activity multipliers, and different default macro ratios. Even two calculators using the same equation can produce different results if they round differently or use slightly different activity multiplier values. Our methodology is fully transparent on this page so you can verify every step. The important thing is consistency: pick one set of targets, follow them for 2-3 weeks, then adjust based on real-world results.
Not exactly. Counting calories tracks only total energy intake. Counting macros tracks the grams of protein, carbohydrates, and fat you eat, which inherently accounts for calories too (protein and carbs = 4 cal/g, fat = 9 cal/g). The advantage of macro counting is body composition control: two 2,000-calorie diets with different macro splits produce very different results. Read our Calorie and Macro Calculator guide for a full comparison.
Research We Rely On
Every formula and recommendation in our calculator is backed by published research. Here are the key studies and resources we reference:
- Mifflin, M.D. et al. (1990). "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 51(2), 241-247. PubMed 2305711
- Frankenfield, D. et al. (2005). "Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults." Journal of the American Dietetic Association, 105(5), 775-789. PubMed 15883556
- Morton, R.W. et al. (2018). "A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength." British Journal of Sports Medicine, 52(6), 376-384. PubMed 28698222
- Jager, R. et al. (2017). "International Society of Sports Nutrition Position Stand: protein and exercise." Journal of the International Society of Sports Nutrition, 14, 20. PubMed 28642676
- U.S. Department of Agriculture & U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. dietaryguidelines.gov
- Helms, E.R. et al. (2014). "A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes." International Journal of Sport Nutrition and Exercise Metabolism, 24(2), 127-138. PubMed 24092765
- Examine.com. "How much protein do you need per day?" examine.com/guides/protein-intake
Contact
Questions, feedback, or suggestions? We'd love to hear from you.
Email: info@macronutrientcalculator.org
Or use our contact form.
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