Macro Calculator

How to use this calculator#

1. 1
   Start from a calorie target you trustMacros are a division of a total, so the total has to be right first. Use your maintenance calories adjusted for your goal — a split applied to a wrong calorie figure gives precise-looking grams of the wrong thing.
2. 2
   Set protein before anything elseProtein is the macro worth defending: roughly 1.6–2.2 g per kilogram of body weight when you are in a deficit or training for muscle. Check that the percentage split you pick actually delivers that in grams, because a 25% protein share of a small calorie target often does not.
3. 3
   Pick a split you can live with, not the most aggressive oneBalanced 30/35/35 suits most people. Low carb 40/20/40 helps some with appetite. High carb 25/55/20 supports heavy training volume. Keto 25/5/70 requires real commitment and is a medical question if you take insulin, sulfonylureas or blood pressure medication.
4. 4
   Convert to food, not just numbersGrams only help if you can hit them. 165 g of protein is roughly six palm-sized portions of meat, fish, eggs, dairy or legumes spread through the day. Working out what your usual meals already supply is more useful than starting from a blank sheet.
5. 5
   Judge the week, not the dayLanding within about 10 g of each target on most days is plenty. Hitting three macros exactly every single day is neither necessary nor, for most people, sustainable.

The formula#

From calories to grams#

Macronutrients carry fixed energy values: protein and carbohydrate supply 4 kcal per gram and fat supplies 9 kcal per gram. To convert a percentage split into grams, multiply your calorie target by the percentage and divide by the calories per gram. Fat always yields fewer grams than its share of calories suggests, which surprises people the first time.

On a 2200 kcal balanced split of 30% protein, 35% carbs and 35% fat, that is 660 kcal of protein divided by 4, giving 165 g; 770 kcal of carbs divided by 4, giving 193 g; and 770 kcal of fat divided by 9, giving just 86 g.

Picking a split you will actually follow#

The balanced 30/35/35 split suits most people. Low carb at 40/20/40 helps some with appetite control, high carb at 25/55/20 supports high training volumes, and the ketogenic 25/5/70 split drops carbohydrate low enough to shift the body toward ketone production. The Zone split of 30/40/30 sits between the extremes.

Total calories drive weight change; the split mainly affects satiety, training performance and how easy the plan is to stick to. Protein is the one macro worth defending, roughly 1.6-2.2 g per kilogram of body weight when losing weight, because it preserves muscle and keeps you full.

Practical cautions#

Very low carbohydrate plans are not suitable for everyone. Anyone taking insulin or sulfonylureas, anyone with kidney disease, and anyone who is pregnant or breastfeeding should not start one without medical supervision, since medication doses often need adjusting. Fat targets that low can also make fat-soluble vitamin intake harder to hit.

These figures are general information, not medical or dietary advice. Round the grams to whatever is convenient, aim to land within about ten grams of each target, and treat consistency over a week as more important than precision on any single day.

Worked examples#

Reference tables#

Common mistakes#

• Dividing fat calories by 4Using 4 kcal/g for fat inflates the gram target by 125%. A 770 kcal fat allowance is 86 g, not 193 g — and eating 193 g of fat would add over 950 kcal to the day, turning a deficit into a surplus.
• Setting protein as a percentage without checking the gramsA 25% protein share sounds generous but delivers only 94 g at 1,500 kcal — about 1.2 g/kg for an 80 kg person, below what supports muscle retention in a deficit. Percentages shrink with the calorie target; grams per kilogram of body weight do not.
• Expecting the split to drive weight changeControlled feeding studies consistently find that when calories and protein are matched, the carbohydrate-to-fat ratio makes little difference to fat loss. The split affects satiety, training performance and adherence — which is where it genuinely matters — not the direction of the scale.
• Starting a very low carbohydrate split while on medicationCutting carbohydrate sharply lowers blood glucose and can drop blood pressure, so insulin, sulfonylurea and antihypertensive doses often need adjusting. Doing this without medical supervision risks hypoglycaemia. Very low carbohydrate diets are also not appropriate in pregnancy or breastfeeding.

Frequently asked questions#

Key terms#

Macronutrient

A nutrient the body needs in large amounts and can obtain energy from: protein, carbohydrate and fat. Alcohol supplies energy too but is not a nutrient.

Atwater factors

The average metabolisable energy values used in food labelling — 4 kcal per gram of protein and carbohydrate, 9 for fat, 7 for alcohol — established by Wilbur Atwater's calorimetry work in the late nineteenth century.

AMDR (acceptable macronutrient distribution range)

The share of total calories from each macronutrient associated with reduced chronic disease risk while still meeting nutrient needs. For adults: 45–65% carbohydrate, 20–35% fat, 10–35% protein.

Net carbohydrate

Total carbohydrate minus fibre, and sometimes minus sugar alcohols. It is a low-carb dieting convention rather than a regulated or universally defined term.

Nutritional ketosis

The metabolic state in which very low carbohydrate intake, typically under about 30 g a day, raises blood ketone concentration as the body shifts toward fat-derived fuel. It is distinct from diabetic ketoacidosis, which is a medical emergency.

IIFYM

'If it fits your macros' — the practice of tracking only macronutrient totals rather than specific foods. It works arithmetically but says nothing about fibre, micronutrients or food quality.

Sources#