Macro Calculator
Know your daily calories, or calculate them from your stats — then choose balanced, low-carb, high-protein, keto, or a custom ratio to see exactly how many grams of protein, carbs, and fat to eat each day and at every meal.
Daily calories
Sex
Ratios always add up to 100% — move one slider and the others rebalance automatically.
Enter your daily calories to see your protein, carbs and fat
This is a very low calorie target. Consider consulting a healthcare professional.
This tool provides educational estimates only — not medical, nutrition, or fitness advice.
Every calculation runs in your browser — nothing is sent to a server.
From calories to grams on your plate
A calorie target tells you how much to eat; macronutrients tell you what that energy is made of. Protein, carbohydrate, and fat are the three energy-providing nutrients, and this calculator splits a daily calorie figure into grams of each — then divides those grams across your meals, which is the number you actually use when planning food.
The split matters because the three macros do different jobs. Protein preserves muscle and keeps you full, carbohydrate fuels higher-intensity activity, and fat supports hormones and the absorption of certain vitamins. Shifting the ratio changes the feel of a diet without necessarily changing its calories.
The two numbers behind every result
First, energy density. Each gram of a macro carries a fixed amount of energy, established by early food-chemistry work and still printed on nutrition labels worldwide:
| Macronutrient | Calories per gram |
|---|---|
| Protein | 4 kcal |
| Carbohydrate | 4 kcal |
| Fat | 9 kcal |
Fat is more than twice as energy-dense, which is why a "low-fat" and a "low-carb" plan of the same calories look so different on the plate. Second, if you don't know your calorie need, the tool estimates it with the Mifflin-St Jeor equation for resting metabolism, multiplied by an activity factor and adjusted for your goal.
Worked example 1 — splitting 2,000 kcal
A balanced 30/40/30 split of 2,000 kcal:
- Protein: 30% × 2,000 = 600 kcal ÷ 4 = 150 g
- Carbs: 40% × 2,000 = 800 kcal ÷ 4 = 200 g
- Fat: 30% × 2,000 = 600 kcal ÷ 9 = 67 g
Across 3 meals that is roughly 50 g protein, 67 g carbs, and 22 g fat per meal.
Worked example 2 — estimating the calorie target
For a 30-year-old man, 178 cm, 75 kg, the Mifflin-St Jeor resting rate is (10 × 75) + (6.25 × 178) − (5 × 30) + 5 = 750 + 1112.5 − 150 + 5 = 1,717.5 kcal. Moderately active (×1.55) gives about 2,662 kcal to maintain, or 2,130 kcal at a 20% cut for weight loss.
How the diet splits compare
The same 2,000 kcal, divided by four common ratios, produces very different gram targets:
| Split (P/C/F) | Protein | Carbs | Fat |
|---|---|---|---|
| Balanced 30/40/30 | 150 g | 200 g | 67 g |
| Low-carb 40/20/40 | 200 g | 100 g | 89 g |
| High-protein 40/40/20 | 200 g | 200 g | 44 g |
| Keto 25/5/70 | 125 g | 25 g | 156 g |
Reading it well
- Percentages always total 100. In custom mode, moving one slider rebalances the others so the split stays valid.
- Protein is often set by body weight rather than a flat percentage; many active people aim for 1.6–2.2 g per kilogram, which you can approximate by adjusting the ratio.
- Grams are rounded for readability, so the three macro calories may not re-add to the exact target down to the last unit.
Not medical advice
These are educational estimates from population formulas, not a personalised nutrition plan. Real needs depend on age, health conditions, training, and goals that a calculator cannot see, and very low targets can be unsafe. Consult a doctor or registered dietitian before making significant dietary changes, especially if you have a medical condition or are pregnant.
Sources & further reading
- Dietary Guidelines for Americans (USDA/HHS) — federal macronutrient and calorie intake recommendations
- USDA Dietary Reference Intakes — energy and acceptable macronutrient distribution ranges
- Academy of Nutrition and Dietetics — protein, carbohydrate, and fat guidance from registered dietitians
- American College of Sports Medicine — nutrition and energy needs for active people and athletes
Frequently asked questions
How many calories are in a gram of protein, carbs, and fat, and why 4/4/9?
Protein and carbohydrates each provide about 4 kilocalories per gram, while fat provides about 9 kilocalories per gram — these are the classic Atwater factors used on nutrition labels worldwide. That's why a diet split described in percentages, like 30% protein / 40% carbs / 30% fat, doesn't translate into equal grams: on a 2,000-kcal day, 30% protein is 600 kcal ÷ 4 = 150 g, but 30% fat is 600 kcal ÷ 9 = only 67 g. This macro calculator does that division automatically for every macro, so you get grams you can weigh on a food scale instead of percentages you'd have to convert yourself.
How is my daily calorie target calculated if I don't know it?
Switch to the 'Calculate my calories' tab and enter your sex, age, height, and weight. The tool first estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation — 10 × weight(kg) + 6.25 × height(cm) − 5 × age, +5 for men or −161 for women — then multiplies it by an activity factor from 1.2 (sedentary) to 1.9 (extra active) to get your total daily energy expenditure. Finally it applies your goal: about 80% of that number for weight loss, 100% to maintain, or roughly 110% for a lean muscle-gain surplus. The result feeds straight into the macro split below, so you never have to copy numbers between calculators.
Which diet split should I choose — balanced, low-carb, high-protein, keto, or custom?
Balanced (30% protein / 40% carbs / 30% fat) suits most general fitness and weight-management goals and is easy to sustain long-term. Low-carb (40/20/40) and keto (25/5/70) cut carbohydrates for people managing blood sugar or following a ketogenic approach, with keto going low enough to typically trigger ketosis. High-protein (40/40/20) favors muscle building or preservation during a calorie deficit, since protein has the highest satiety and helps protect lean mass. If none of the presets fit, choose Custom and drag the three sliders — they always rebalance to add up to 100%, so you can dial in exactly the ratio your coach or dietitian recommends.
What does IIFYM mean, and does this calculator support flexible dieting?
IIFYM stands for 'if it fits your macros' — a flexible-dieting approach where you can eat any food, as long as its protein, carbs, and fat add up to your daily targets. The Custom split mode is built for exactly this: set your own protein, carb, and fat percentages, for example based on a coach's recommendation, and this macro calculator turns them into grams you can track in any food-logging app. Keep in mind this tool computes calorie and macro targets only — it doesn't account for fiber, micronutrients, or food quality, so IIFYM works best alongside otherwise reasonably nutritious eating rather than as a substitute for it.
Is this medical advice, and does my data leave my browser?
No to both. Every calculation — the BMR estimate, the calorie target, and the macro split — runs entirely in your browser using the numbers you type; nothing is uploaded, logged in, or sent to any server, and your last inputs are saved only in your browser's local storage for next time. This calculator provides educational, formula-based estimates for general fitness and nutrition planning, not personalized medical, dietary, or clinical advice — if you have a health condition, are pregnant, or want a plan tailored to you, please consult a doctor or registered dietitian.