Macro Calculator

The calculator first works out your Basal Metabolic Rate using the Mifflin-St Jeor equation, which is the most accurate BMR formula for the general population. It then multiplies your BMR by an activity factor (1.2 for sedentary up to 1.9 for extremely active) to get your Total Daily Energy Expenditure, then adjusts up or down based on your goal.

The maths in plain numbers: a 30-year-old male, 175cm, 75kg has a BMR of about 1,673 calories. At a moderately active job (factor 1.55) that is a TDEE of 2,593 calories. To lose weight at a 20% deficit, you eat 2,074. To lean bulk at a 10% surplus, you eat 2,852. Calories are then split into grams of protein, carbs and fat using your chosen diet ratio. Protein and carbs each have 4 calories per gram; fat has 9 calories per gram, which is why even small amounts of fat add up fast.

There is no single best split. The right macros depend on what you are training for and which foods you actually enjoy eating. The calculator offers nine pre-set diets covering keto (5% carbs, 70% fat), high protein (40% protein), Mediterranean (50% carbs, lots of olive oil), vegan (50% carbs, 25% protein), and others including a custom option.

Real world rules of thumb: if you are losing weight and lifting weights, you want at least 1.6g of protein per kg of body weight to keep muscle. If you are doing endurance work (long runs, cycling), you need carbs above 50% of total calories. If you are sedentary and trying to manage blood sugar, lower-carb splits like Low Carb or Mediterranean tend to work better. The biggest mistake is picking the most aggressive split (full keto, 1g/lb protein) when a moderate split would be far easier to actually stick to. The diet you can keep up for 6 months beats the diet you abandon in 3 weeks.

The legally required minimum (RDA) is 0.8g per kg of body weight, but research on muscle protein synthesis points to a higher target: 1.6 to 2.2g per kg if you are building or maintaining muscle, and 1.2 to 1.6g per kg for general fitness and health.

For a 75kg person, that is 120 to 165g of protein per day for muscle building, or 90 to 120g for general health. Spread across 3 to 5 meals so each meal hits 25 to 40g, which is the amount needed to maximise muscle protein synthesis per sitting. Practical examples: 150g chicken breast (45g protein), 200g Greek yoghurt (20g), three eggs (18g), one scoop of whey (25g). If you struggle to hit your target on whole foods alone, a daily protein shake covers the gap. Pair this calculator with the [calorie deficit calculator](/calorie-deficit-calculator) and the [TDEE calculator](/tdee-calculator) for a full picture of your nutrition plan.

Recalculate every time your weight changes by more than 5kg, or after about 3 months on the same plan. Your BMR drops as you lose weight (a smaller body needs fewer calories), so a calorie target that worked at 90kg will be too high once you reach 80kg.

The most common reason people stop losing weight is that their body has adapted to the new lower calorie level and they have not adjusted again. Re-run this calculator with your current weight and trim another 100 to 200 calories from the daily target if the scale has stalled for more than 3 weeks. Equally important: if you are bulking and the scale has been flat for 2 weeks, add 150 to 200 calories. Tracking accuracy slips over time too. If you have stopped weighing food, re-weigh your portions for a few days and you will often find what you thought was 100g is actually 130g.