Macro Calculator — protein, carbs & fat for your goal

The macro calculator below turns your weight, height, age, and activity level into a daily calorie target and a gram-by-gram breakdown of protein, carbs, and fat. Instead of guessing what to eat, you get three numbers to hit — and hitting them consistently matters far more than any single "perfect" meal.

Arb Digital built this tool the way we build everything: no login, no email wall, no upsell — just a calculator that works. Punch in your numbers, pick a goal, and the breakdown updates instantly.

What This Macro Calculator Does

It estimates your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, multiplies it by an activity factor to get your Total Daily Energy Expenditure (TDEE), then adjusts that number up or down based on whether you're cutting, maintaining, or bulking. From there it sets your protein intake first — because protein is the macro that determines whether the weight you gain or lose is muscle or fat — then fills the rest of your calories with fat and carbohydrates.

This is the same basic math a dietitian or coach would use as a starting point. It won't replace a lab-measured metabolic test, but it gets you within a realistic range that you can adjust after two or three weeks of real-world results.

How to Use It

1. Pick your units. Switch between imperial (lb/in) and metric (kg/cm) — the calculator converts automatically.
2. Enter weight, height, and age. Use your current stats, not a target weight.
3. Select gender. This affects the BMR formula, since men and women carry different average amounts of lean mass at the same weight.
4. Choose your activity level. Be honest — most people overestimate how active they actually are.
5. Pick a goal. Cut subtracts 20% from maintenance calories, bulk adds 10%, and maintain keeps you at your TDEE.
6. Set a protein target. 0.8 g/lb is a solid baseline, 1.0 g/lb is the common recommendation for anyone lifting weights, and 1.2 g/lb suits aggressive cutting or older adults preserving muscle.
7. Read your macros. The big number is your daily calorie target; the grid below shows protein, carbs, and fat in grams plus your percentage split.

The Formula Behind the Numbers

BMR is calculated with the Mifflin-St Jeor equation, which the Academy of Nutrition and Dietetics has repeatedly found to be the most accurate predictive formula for the general population (compared with older equations like Harris-Benedict). For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women, subtract 161 instead of adding 5. That BMR is multiplied by an activity factor between 1.2 and 1.9 to estimate TDEE — the calories you burn in an average day including movement and exercise. See the USDA Dietary Reference Intake calculator for a government-run reference point on daily energy needs.

Once TDEE is set, the goal adjustment shifts calories by a fixed percentage — a moderate, sustainable rate rather than an extreme crash-diet cut. Protein is calculated first in grams per pound of body weight, converted to calories at 4 calories per gram. Fat is set at 25% of total calories (9 calories per gram), a level that supports hormone health without crowding out other macros. Whatever calories remain go to carbohydrates at 4 calories per gram — the flexible, refuel-your-training macro.

Why Protein Is the Macro That Actually Matters

Of the three macronutrients, protein does the heavy lifting for body composition. When you're in a calorie deficit, your body needs a reason to hold onto muscle instead of burning it for fuel alongside fat — and adequate protein, combined with resistance training, is that reason. Research summarized by the NIH Office of Dietary Supplements consistently shows that higher protein intakes during weight loss help preserve lean mass better than lower-protein, calorie-matched diets. That's the whole reason this calculator asks for a protein target before it touches anything else.

On the flip side, if you're bulking, protein is what turns surplus calories into muscle rather than just body fat. A gram-per-pound target gives your body the raw material it needs to repair and build tissue after training. Skimp on protein during a bulk and a bigger share of the extra calories ends up as fat gain instead of muscle.

Flexible Dieting (IIFYM) and Why It Works

"If It Fits Your Macros" (IIFYM) is a popular approach built on exactly the numbers this calculator produces: hit your protein, carb, and fat targets for the day, and the specific foods you eat to get there are up to you. It works because it removes the all-or-nothing thinking that derails most diets — a slice of pizza isn't "cheating," it's just carbs and fat that count against your daily numbers like anything else.

The appeal of flexible dieting is sustainability. Rigid meal plans fail the moment real life gets in the way — a birthday party, a business trip, a bad day. Macro targets bend with you. You can eat out, have dessert, or skip a planned meal and still land in your numbers by adjusting the rest of the day. That flexibility is a big part of why people who track macros tend to stick with it longer than people on restrictive diets.

Why "Eat Less" Without Enough Protein Backfires

The most common diet mistake isn't eating too many calories — it's cutting calories without protecting protein intake. When total food intake drops but protein stays low, the body pulls from muscle tissue to make up the energy shortfall, especially if training also drops off. The result is a lower number on the scale that's made up of more lost muscle and less lost fat than the person intended — plus a metabolism that slows down more than it needed to, because muscle is metabolically active tissue.

This is why simply "eating less" is bad advice on its own. Two people can eat the same total calories and get very different results depending on where those calories come from. Someone eating 1,600 calories with 150g of protein will generally preserve more muscle — and look and feel better at the same body weight — than someone eating 1,600 calories with 60g of protein and the rest split between carbs and fat.

How to Actually Hit Your Macros Day to Day

Numbers on a screen only help if you can translate them into meals. A practical starting point is to build each plate around a protein source first — chicken, fish, eggs, tofu, Greek yogurt, lean beef — sized to roughly a quarter to a third of your daily protein target per meal. From there, add a carbohydrate source sized to your activity that day, and round it out with fat from cooking oil, nuts, avocado, or the natural fat already in your protein choice. Tracking apps can log this automatically once you know your daily gram targets, but even a rough mental habit of "protein first, then carbs and fat around it" gets most people most of the way there without obsessive weighing.

It also helps to think in terms of a weekly average rather than a daily grade. If Tuesday's dinner runs a little heavy on carbs, Wednesday can lean a little lighter — your body responds to trends over days and weeks, not to any single meal. This is part of why flexible dieting sustains itself better than rigid meal plans: it gives you room to be human without derailing the whole approach.

Common Mistakes to Avoid

• Guessing your activity level too high. A desk job with a gym session three times a week is usually "light," not "moderate" or "active."
• Setting fat too low. Dropping fat intake under roughly 20% of calories for long stretches can disrupt hormone production, especially in women.
• Chasing protein at the expense of everything else. More than about 1.2-1.5 g/lb rarely adds extra benefit and just crowds out carbs your training needs.
• Not reassessing. Your TDEE changes as your weight changes — recalculate every few weeks, not once and forget it.
• Confusing net carbs with total carbs. This calculator outputs total carbohydrate grams; adjust manually if you're tracking net carbs for a specific diet style.
• Weighing yourself daily and reacting to every fluctuation. Sodium, water, and hormones can shift the scale by several pounds; judge progress over weekly averages instead.

Related Free Tools From Arb Digital

Once you have your macros, check your calorie & TDEE calculator results for context, estimate your lean body mass to see how much of your weight is muscle versus fat, calculate your BMR across multiple formulas, or see your ideal weight range. You can also check your body fat percentage. Browse our full free online tools hub for more.

Frequently Asked Questions

This tool provides general estimates for educational purposes only and is not medical advice. Individual needs vary — consult a doctor or registered dietitian before making health, nutrition, or fitness decisions.