How your macros are calculated
First the calculator works out your daily calorie target from your BMR, activity level and goal (see the calorie calculator for the full method). Then it splits those calories the same way the NutriSmart app does:
- Protein: 1.85 g per kg of body weight (2.2 g/kg if your goal is to build muscle). Protein is set from your weight, not as a percentage, because your muscles need about the same amount whether you eat 1,500 or 2,500 calories.
- Fat: 25% of your calories. Enough for hormones and the absorption of vitamins A, D, E and K, and inside the 20–35% range recommended by the Dietary Guidelines for Americans.
- Carbs: everything that’s left. Carbs fuel training and daily activity, so they take the remaining calories.
To turn calories into grams: protein and carbs have 4 kcal per gram, fat has 9 kcal per gram.
Example
A 30-year-old woman, 68 kg (150 lb), lightly active, losing weight at the standard pace has a target of 1,540 kcal a day. Her macros:
| Macro | Grams per day | Calories | Share |
|---|---|---|---|
| Protein | 68 × 1.85 = 126 g | 503 kcal | 33% |
| Fat | 1,540 × 25% ÷ 9 = 43 g | 385 kcal | 25% |
| Carbs | (1,540 − 503 − 385) ÷ 4 = 163 g | 652 kcal | 42% |
Why protein comes first
When you eat in a calorie deficit, the body can break down muscle as well as fat. Eating more protein – combined with some strength training – keeps more of that muscle. A large meta-analysis found that the benefits for muscle level off at about 1.6 g per kg a day, with some people benefiting up to 2.2 g/kg (Morton et al., 2018). Protein is also the most filling macro, which helps when you’re eating less. More in the protein calculator.
How to hit your macros with real food
Approximate values per 100 g (raw, unless stated):
| Food | Protein | Carbs | Fat | Calories |
|---|---|---|---|---|
| Chicken breast, skinless | 23 g | 0 g | 2 g | 120 kcal |
| Eggs (about 2) | 13 g | 1 g | 10 g | 143 kcal |
| Greek yogurt, plain 2% | 10 g | 4 g | 2 g | 73 kcal |
| Lentils, cooked | 9 g | 20 g | 0.4 g | 116 kcal |
| Rolled oats | 13 g | 68 g | 7 g | 379 kcal |
| Rice, cooked | 3 g | 28 g | 0.3 g | 130 kcal |
| Olive oil | 0 g | 0 g | 100 g | 884 kcal |
Values from USDA FoodData Central; brands and cooking methods vary.
A simple way to build a day: start each meal with a protein source (about a quarter of your daily protein per meal), add vegetables, then fill the rest with carbs and fats until you reach your calories.
Tracking macros without the spreadsheet
Weighing and logging every ingredient is where most people give up. NutriSmart sets these same macro targets for you, then counts protein, carbs and fat from a photo of what you eat or a barcode scan, and shows what’s left for the day.
The results are estimates for healthy adults aged 18–80 and are not medical advice. If you have kidney disease, diabetes or another medical condition, ask your doctor or a registered dietitian before changing your diet.
Frequently asked questions
What are macros?
Macros (macronutrients) are the three nutrients that provide calories – protein (4 kcal per gram), carbohydrates (4 kcal per gram) and fat (9 kcal per gram). Counting macros means tracking grams of each, not just total calories.
What is the best macro ratio for weight loss?
There is no single best ratio – total calories decide weight loss. What helps most is enough protein (about 1.6–2.2 g per kg of body weight) to protect muscle and keep you full, at least 20% of calories from fat, and the rest from carbs you enjoy and can stick with.
Do I need to hit my macros exactly?
No. Being within about 10 grams of your protein target and roughly on your calorie target each day is plenty. Carbs and fat can move around from day to day as long as the total calories stay in place.
Why is my protein higher than the usual 10–35% guideline?
General guidelines are for people eating at maintenance. When you eat less to lose weight, your calories go down but your body still needs the same protein to keep muscle, so protein naturally makes up a bigger share of a smaller total.
Can I use this macro calculator for keto or low-carb?
The calculator gives a balanced split. For keto, keep the protein and calorie targets, limit carbs to about 20–50 g a day and get the remaining calories from fat.