Macro Calculator

Calculate your exact daily macros — protein, carbs, and fat — based on your body stats, activity level, and goal. Uses the Mifflin-St Jeor formula.

Free No signup required Instant results Evidence-based formula

What Are Macros and Why Do They Matter?

Macronutrients — or "macros" — are the three main categories of nutrients that make up the caloric content of food: protein, carbohydrates, and fats. Unlike micronutrients (vitamins, minerals), macros are measured in grams and are the primary source of energy for your body.

Understanding your macros goes beyond just counting calories. Two people can eat the same number of calories but achieve completely different body composition results based on how those calories are split between protein, carbs, and fat.

How to Use Your Macro Results

Once you have your daily macro targets, the next step is tracking them. Apps like MyFitnessPal, Cronometer, or our own free calculators make this straightforward. Here's what to do:

Log everything you eat for the first 2 weeks to learn the macro content of your common foods
Prioritise hitting your protein target first — it's the most impactful macro for body composition
Fill remaining calories with carbs and fats based on preference and energy needs
Reassess every 4 weeks and adjust calories by 100–200 kcal if progress has stalled

The Mifflin-St Jeor Formula Explained

This calculator uses the Mifflin-St Jeor equation, considered the most accurate BMR formula for the general population. Developed in 1990, it's validated by multiple studies and used by registered dietitians worldwide.

The formula is:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

Your BMR is then multiplied by an activity factor (1.2 to 1.9) to estimate TDEE. Your target calories are adjusted based on your goal: −500 kcal for weight loss, +500 kcal for muscle gain.

Frequently Asked Questions

What are macros in nutrition?

Macros (macronutrients) are the three main nutrients your body needs in large amounts: protein, carbohydrates, and fat. Each provides energy — protein and carbs give 4 calories per gram, fat gives 9 calories per gram.

How does the macro calculator work?

The calculator uses the Mifflin-St Jeor equation to estimate your BMR (Basal Metabolic Rate), multiplies it by your activity level to get TDEE, then adjusts calories based on your goal. Macros are split using evidence-based ratios.

What macro split should I use for weight loss?

For weight loss, a 35% protein / 35% carbs / 30% fat split works well. Higher protein preserves muscle during a calorie deficit. Our calculator uses this split automatically when you select "Lose Weight".

How much protein do I need per day?

Most research suggests 1.6–2.2g of protein per kg of bodyweight for muscle preservation and growth. Our calculator sets protein at roughly 35% of target calories for weight loss goals.

Can I use this macro calculator for keto?

This calculator uses balanced macro splits. For a strict keto diet (70% fat, 25% protein, 5% carbs), use our dedicated Keto Macro Calculator which is optimised for ketogenic ratios.

What is a calorie deficit?

A calorie deficit means eating fewer calories than your body burns (TDEE). Our calculator creates a 500 kcal deficit for weight loss, which is the safe and sustainable rate of ~0.5 kg per week.

How accurate is the macro calculator?

The Mifflin-St Jeor formula is accurate within 10% for most people. Individual metabolism varies, so use the numbers as a starting point and adjust after 2–3 weeks based on actual results.

Should I count macros or just calories?

Counting macros gives you more control over body composition — ensuring enough protein to preserve muscle and enough fat for hormone health. For beginners, start by just tracking protein, then add carbs and fat tracking.