Macro Calculator
Calculate your daily protein, carbs, and fat targets using the Mifflin-St Jeor equation. Adjust for your activity level and goal — results are instant, no email required.
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How This Macro Calculator Works
This calculator uses a three-step process to determine your optimal macronutrient targets: calculate BMR, adjust for activity, then allocate macros by goal.
Step 1: Basal Metabolic Rate (BMR)
Your BMR is the number of calories your body burns at complete rest — just to keep your heart beating, lungs breathing, and cells functioning. We use the Mifflin-St Jeor equation (1990), which is the most accurate BMR formula available for the general population:
Male: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Female: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Step 2: Total Daily Energy Expenditure (TDEE)
Your TDEE accounts for the calories you burn through daily movement and exercise. It's calculated by multiplying your BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active).
Step 3: Goal Adjustment & Macro Split
Your TDEE is adjusted based on your goal: a 20% calorie deficit for weight loss, maintenance calories for maintaining weight, or a 10% surplus for muscle gain. Macros are then allocated using evidence-based ratios that optimize for each goal.
Understanding Your Macro Results
Proteinis the most important macro to track. It's the building block of muscle tissue and the most satiating macronutrient — meaning it helps you feel full. At 4 calories per gram, hitting your protein target is especially important during a calorie deficit to prevent muscle loss.
Carbohydratesare your body's preferred fuel source, especially during high-intensity exercise. At 4 calories per gram, carbs power your workouts and replenish muscle glycogen stores. This calculator allocates more carbs for muscle gain goals, where performance and energy are priorities.
Fatis essential for hormone production, including testosterone and estrogen, and for absorbing fat-soluble vitamins (A, D, E, K). At 9 calories per gram it's more calorie-dense, so even a 20% allocation covers your essential fat needs.
Tips for Hitting Your Macros
- 1Track protein first. If you hit nothing else, hit your protein target. Research shows that equating protein while varying carb/fat ratios produces similar body composition outcomes.
- 2Use a food scale. Volume measurements of protein sources (chicken, beef, fish) can vary by 30–50% depending on how tightly food is packed.
- 3Log consistently for 2–3 weeks. Most people find that after a few weeks, they can eyeball their macros accurately enough without logging every meal.
- 4Recalculate every 10–15 lbs. As your body weight changes, your TDEE shifts and your macro targets should be updated accordingly.
Frequently Asked Questions
What are macros?
Macros (macronutrients) are the three main nutrients your body uses for energy: protein (4 kcal/g), carbohydrates (4 kcal/g), and fat (9 kcal/g). Tracking macros lets you hit specific targets for each nutrient rather than just counting total calories.
How does this macro calculator work?
This calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), multiplies it by your activity level to get your Total Daily Energy Expenditure (TDEE), then adjusts calories by your goal (−20% for loss, +10% for gain). Macros are split by evidence-based ratios: 40/40/20 for fat loss, 30/40/30 for maintenance, 30/45/25 for muscle gain.
How much protein should I eat?
For muscle building or fat loss, research consistently supports 1.6–2.4g of protein per kilogram of body weight per day. Sedentary individuals can get by with 0.8g/kg. Higher protein intakes preserve muscle mass during a calorie deficit.
What is Mifflin-St Jeor and why use it?
The Mifflin-St Jeor equation (1990) is the most accurate BMR formula for the general population, outperforming the older Harris-Benedict equation by approximately 5% in accuracy. It's the equation recommended by the Academy of Nutrition and Dietetics.
Should I track macros or just calories?
For most people, tracking protein is the highest-leverage macro. If you hit your protein target and overall calorie goal, carb/fat ratios matter less day-to-day. Full macro tracking is most useful during body recomposition or competition prep.
How often should I recalculate my macros?
Recalculate every 10–15 lbs of body weight change, or if your activity level shifts significantly. As you lose weight, your TDEE decreases — so your targets need to be updated to continue making progress.