Macros — short for macronutrients — are the three main components of your diet that provide energy: protein, carbohydrates and fats. Each gram of protein and carbohydrate contains around 4 calories, while each gram of fat contains around 9 calories. Tracking your macros gives you a much clearer picture of your nutrition than counting calories alone, because the balance between protein, carbs and fats affects everything from appetite and energy levels to muscle retention during weight loss.

Protein supports muscle repair, immune function and satiety. During weight loss, a higher protein intake helps preserve lean muscle mass and keeps you feeling fuller for longer. Sources include chicken, fish, eggs, Greek yoghurt, tofu, lentils and beans.

Carbohydrates are your body’s preferred source of energy, particularly for the brain and during exercise. Focus on complex carbohydrates like oats, wholegrain bread, brown rice, sweet potatoes, fruit and vegetables. The NHS recommends that starchy carbohydrates make up just over a third of the food you eat.

Fats are essential for hormone production, brain health and absorbing fat-soluble vitamins (A, D, E and K). Prioritise unsaturated fats from sources like olive oil, avocados, nuts, seeds and oily fish, while limiting saturated fats from processed foods.

The macro and calorie counter uses a three-step calculation that mirrors the methodology used by dietitians and sports nutritionists.

Step 1 — Basal Metabolic Rate (BMR). Your BMR is the number of calories your body burns at complete rest, just to keep you alive — breathing, circulating blood, and maintaining body temperature. The calculator uses the Mifflin-St Jeor equation, recognised as one of the most accurate predictive equations for resting energy expenditure in adults.

Step 2 — Total Daily Energy Expenditure (TDEE). Your TDEE is your BMR multiplied by an activity factor that reflects how active you are during a typical day. This gives a realistic picture of the total calories you burn, including exercise and everyday movement.

Step 3 — Goal adjustment and macro split. Based on your goal — fat loss, maintenance or muscle gain — the calculator applies a calorie deficit or surplus to your TDEE and then divides those calories into a recommended split of protein, carbs and fats designed to support your goal.

Counting calories alone tells you how much you are eating, but tracking macros tells you what you are eating. Two people could eat the exact same number of calories and get very different results depending on how those calories are distributed across protein, carbs and fats. Tracking your macros can help you:

• Lose fat while preserving muscle mass
• Reduce hunger and cravings by eating enough protein and fibre
• Improve energy levels and exercise performance
• Build a healthier, more balanced relationship with food
• Stay on track during weight loss treatment with Mounjaro, Wegovy or other GLP-1 medications

If you are taking a weight loss injection like Mounjaro (tirzepatide) or Wegovy (semaglutide), your appetite will be significantly reduced. This makes it more important than ever to make every calorie count. A common challenge during GLP-1 treatment is not eating enough protein, which can lead to muscle loss alongside fat loss.

Using the macro calculator UK helps you set a realistic daily protein target — typically 1.2 to 2.0 grams of protein per kilogram of body weight for adults pursuing fat loss — so you can structure smaller meals that still deliver the nutrients your body needs. The British Dietetic Association publishes a range of free food and nutrition fact sheets to support healthy eating choices.

Once you have your numbers, the next step is putting them into practice.

Track using a food diary or app. Apps like MyFitnessPal, Cronometer and Nutracheck allow you to log meals and automatically calculate your daily macros. Most have free versions.

Weigh your food where possible. Eyeballing portions tends to underestimate calorie intake significantly. A set of digital kitchen scales is one of the most useful tools for accurate tracking.

Aim for consistency, not perfection. Hitting your macros exactly every day is unrealistic. Focus on hitting your protein target consistently, keeping calories within roughly 100 to 150 of your goal, and being flexible with carbs and fats around your preferences.

Reassess every 4 to 6 weeks. As your weight changes, so will your calorie needs. Recalculate your macros every few weeks — particularly if you are losing weight on a GLP-1 medication — to make sure your targets stay accurate.

Yes — the macro and calorie counter is completely free and does not require an account or any personal information beyond what is needed for the calculation.

The calculator uses the Mifflin-St Jeor equation, which research has shown to be one of the most accurate predictive equations for resting metabolic rate in healthy adults. However, all calculators provide an estimate — individual metabolism varies, and you may need to adjust your targets based on real-world results.

A calorie deficit of 500 calories per day below your TDEE typically supports a weight loss of around 0.5 kg (1 lb) per week, which the NHS recommends as a safe, sustainable rate of weight loss. The macro calculator UK applies this principle automatically when you select a fat loss goal.

Yes. The calculator is a useful starting point for anyone on a GLP-1 weight loss injection. Because your appetite will be reduced, focusing on hitting your protein and fibre targets first is especially important. For personalised advice, speak to our clinical team via a free online consultation.

Not necessarily. Many people track macros consistently for a few months to learn portion sizes and food composition, then move to a more intuitive approach once those habits are established.