Calories decide whether weight changes; macros decide what it's made of. This calculator converts a daily calorie target into grams of protein, carbs and fat using the Atwater factors — 4 kcal per gram of protein and carbohydrate, 9 for fat.
Worked example
2,000 kcal on the balanced 30/40/30 preset: protein 2,000×0.30÷4 = 150 g, carbs 2,000×0.40÷4 = 200 g, fat 2,000×0.30÷9 = 67 g. Fat's gram count always looks small — it packs more than double the energy per gram.
Choosing a split
Official guidance is a wide corridor: 10–35% protein, 45–65% carbs, 20–35% fat. Inside it, evidence supports personal preference. High-protein splits (the 40/30/30 preset) protect muscle in a deficit; endurance athletes bias carbs; low-carb approaches (30/20/50) simply route more energy through fat. The two sliders auto-balance — fat absorbs the remainder so the shares always total 100%.
Protein deserves the anchor role
Research on active adults supports 1.6–2.2 g per kg of body weight — well above the 0.8 g/kg survival baseline. A practical approach: set protein from body weight first, then divide the remaining calories between carbs and fat by preference. The per-meal line shows the 3-meal split, since distributing protein across the day beats loading it at dinner.
Get the calorie number right first
Macros inherit their accuracy from the calorie target. Compute maintenance with the TDEE calculator, adjust for your goal (−500 kcal ≈ 0.5 kg/week loss), and bring the result here. Body-composition context lives in the body fat and lean body mass calculators.
General guidance for healthy adults; not medical or dietetic advice.