Macro Calculator (IIFYM)
Enter your body stats, activity level and goal. You get a daily calorie target and how many grams of protein, carbs and fat to eat, per day and per meal, for the diet split you choose.
Per meal (4 meals)
| Per day | Per meal | Calories/meal |
|---|
Disclaimer: these numbers are estimates for healthy adults and are not medical advice. If you are pregnant, under 18, have a medical condition or a history of disordered eating, talk to a doctor or registered dietitian before changing your diet.
How to use the Macro Calculator (IIFYM)
- Choose units and sex, then enter your age, height and weight. Add body fat % if you know it.
- Pick your activity level and your goal: lose, maintain or gain, with a weekly rate.
- Choose a diet split preset or switch to Custom and drag the sliders.
- Set meals per day to see how much protein, carbs and fat to eat at each meal.
- Read your targets and press Copy to save them in your notes or food tracking app.
The formulas behind your macros
Mifflin-St Jeor BMR (weight in kg, height in cm, age in years):
- Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
- Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
Katch-McArdle BMR = 370 + 21.6 × lean body mass (kg), where lean mass = weight × (1 − body fat %).
TDEE = BMR × activity factor (1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 extra active). Your calorie goal = TDEE minus a deficit to lose weight, or plus a surplus to gain. One kilogram of body fat is often estimated at about 7,700 kcal (about 3,500 kcal per pound), so losing 0.5 kg a week needs roughly 550 kcal a day below TDEE.
Worked example: a 30-year-old man, 178 cm, 80 kg, moderately active. BMR = 800 + 1,112.5 − 150 + 5 = 1,767.5 kcal. TDEE = 1,767.5 × 1.55 ≈ 2,740 kcal. On a balanced 30/40/30 split that is about 205 g protein, 274 g carbs and 91 g fat.
Popular macro splits compared
| Split | Protein | Carbs | Fat | Good for |
|---|---|---|---|---|
| Balanced / Zone | 30% | 40% | 30% | General fitness, an easy starting point |
| High protein | 40% | 30% | 30% | Fat loss while keeping muscle, staying full |
| Low carb | 40% | 20% | 40% | People who prefer fewer starches and sugars |
| Keto | 25% | 5% | 70% | Ketogenic diets (usually under 50 g carbs a day) |
The Acceptable Macronutrient Distribution Ranges (AMDR) set by the US National Academies for adults are 10–35% of calories from protein, 45–65% from carbohydrate and 20–35% from fat. Low-carb and keto splits fall outside these ranges by design, so they are best followed with some planning.
Tips for hitting your macros
- Start with protein. Build each meal around a protein source, then fill in carbs and fat.
- Use a food scale for a week or two. Estimating portions by eye is often off by 20% or more.
- Get enough fiber. About 14 g per 1,000 kcal from vegetables, fruit, legumes and whole grains supports digestion and fullness.
- Re-calculate as you change. As your weight drops, your TDEE drops too. Update your numbers every 4–5 kg (about 10 lb).
- Judge by trends. Track your average weight over 2–3 weeks before changing calories.
Frequently asked questions
What does IIFYM mean?
IIFYM stands for "If It Fits Your Macros". It is a flexible dieting approach where you hit daily targets for calories, protein, carbohydrates and fat, rather than following a fixed list of allowed foods.
How are calories converted to grams of macros?
Protein and carbohydrates provide about 4 kcal per gram and fat provides about 9 kcal per gram. For 2,000 kcal at 30% protein, that is 600 kcal ÷ 4 = 150 g of protein.
Which BMR formula does this calculator use?
It uses the Mifflin-St Jeor equation, which is considered the most accurate everyday formula for most adults. If you enter your body fat percentage, it switches to the Katch-McArdle formula, which is based on lean body mass.
How big should my calorie deficit be?
A loss of about 0.5 kg (1 lb) per week, roughly a 500 to 550 kcal daily deficit, is a common sustainable target. Faster rates are possible but make it harder to keep muscle and stick with the plan.
Which macro split is best?
For weight change, total calories matter most. Within that, enough protein helps preserve muscle and keeps you full, and the carb and fat balance can follow your preference. Pick the split you can stick with.
Why are Balanced and Zone the same split?
The Zone diet uses 40% carbs, 30% protein and 30% fat, which matches the balanced 30/40/30 split used here. They differ in food choices and meal structure rather than in the macro percentages.