Macro Calculator
Work out your daily protein, carbs and fat targets from your age, height, weight and activity level — using the Mifflin-St Jeor equation, entirely in your browser.
What is a macro calculator?
Macronutrients — protein, carbohydrates and fat — are the three nutrients your body needs in large amounts, and they supply all of your calories. A macro calculator works out how many grams of each you should eat in a day to reach a specific goal, whether that is losing weight, maintaining, or building muscle.
It starts by estimating your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, which is based on your height, weight, age and sex. BMR is multiplied by an activity factor to give your Total Daily Energy Expenditure (TDEE) — the calories you burn each day. A goal adjustment is applied, then the remaining calories are split between protein, carbs and fat according to the ratio you choose. Because protein and carbs supply 4 calories per gram and fat supplies 9, the calculator converts those calorie shares into grams.
Everything runs locally on your device, so your body details are never uploaded anywhere.
How to use
- Select your sex and enter your age, height and weight.
- Choose your activity level, then pick your goal (lose, maintain or gain).
- Pick a macro split, then click Calculate macros to see your daily calories and gram targets.
Example
A 30-year-old woman who is 165 cm and 65 kg, moderately active, wants to maintain weight. Her BMR is (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 1,366. Times 1.55 gives a TDEE of about 2,117 calories. Using a balanced 30/40/30 split, that becomes roughly 159 g of protein, 212 g of carbs and 71 g of fat per day.
Common use cases
- Setting daily targets for weight loss or muscle gain.
- Planning meals around a flexible dieting approach.
- Building a keto or low-carb meal plan.
- Making sure you hit enough protein while cutting.
Pro tips
- Aim for a 250-500 calorie deficit for slow, sustainable fat loss rather than aggressive cutting.
- Keep protein high — around 1.2-1.6 g per kg of body weight — to preserve muscle.
- Re-calculate every few weeks as your weight changes.
- Use a food scale to track your macros accurately at first.
FAQ
What is a macro calculator?
A macro calculator estimates how many grams of protein, carbohydrates and fat you should eat each day, based on your body, activity level and health goal.
How do I calculate my macros for weight loss?
Find your maintenance calories, subtract a 250-500 calorie deficit, then split the remaining calories between protein, carbs and fat using your chosen ratio.
How many calories are in a gram of protein, carbs and fat?
Protein and carbohydrates both provide 4 calories per gram, while fat provides 9 calories per gram.
What is the best macro ratio for muscle gain?
Most people building muscle do well with roughly 30% protein, 40% carbs and 30% fat, alongside a small calorie surplus and progressive strength training.
What is TDEE and how do you find it?
Total Daily Energy Expenditure (TDEE) is the calories you burn in a day. It is your BMR multiplied by an activity factor, and it is the starting point for setting macros.
Do I have to track macros to lose weight?
No — a calorie deficit is what drives weight loss. Tracking macros simply helps you hit that calorie target while keeping protein high enough to preserve muscle.
What are good macros for a keto diet?
A ketogenic macro split is typically around 25% protein, 5% carbs and 70% fat, which keeps carbs low enough to stay in ketosis.
Is this macro calculator accurate?
The Mifflin-St Jeor equation is a research-backed estimate, but your actual needs vary, so treat the results as a starting point and adjust based on progress.
How much protein per kg of body weight do I need?
For most healthy adults 1.2-1.6 g per kg of body weight supports recovery and muscle retention; higher intakes suit active people and those building muscle.
What is the Mifflin-St Jeor equation?
It calculates BMR as 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5 for men, or - 161 for women. It is widely used to estimate resting calorie needs.
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