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Macro Calculator

Estimate your daily calorie target with the Mifflin-St Jeor equation, then split it into grams of protein, carbohydrate and fat using a preset ratio or your own percentages.

The equation uses a fixed offset by sex (+5 for men, −161 for women).
Adults only — the equation was derived from people aged 19–78.
Only know stones or pounds? Convert first with the unit converter.
Conventional multipliers, the same set as our Calorie Calculator. See Sources for the FAO/WHO/UNU activity bands they approximate.
Filled in by the goal above. Edit it for a gentler or steeper change — a negative number is a deficit.
Balanced and higher-protein sit inside the AMDR reference ranges; lower-carb drops carbohydrate below them (the result flags this).

Macro split — the share of your daily calories going to each macronutrient. Pick a preset or type your own; the three must add up to 100%.

—
BMR (resting energy, Mifflin-St Jeor)—
Maintenance calories (TDEE)—
Daily target—
Protein—
Carbohydrate—
Fat—
Protein per kg of body weight—

This is an estimate for healthy adults, not a clinical plan or medical advice. The equation predicts a population average, so your real needs can differ by a few hundred calories either way. Talk to a GP or registered dietitian before changing your diet, especially if you are pregnant, under 18, or have a medical condition. Nothing you type leaves your browser — the calculation runs entirely on this page.

How the estimate is built

Step 1 — resting energy (BMR). Mifflin-St Jeor (1990): 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years), then +5 for men or −161 for women. The equation was fitted to 498 healthy adults aged 19–78 measured by indirect calorimetry.

Step 2 — maintenance calories (TDEE). BMR multiplied by an activity factor. The FAO/WHO/UNU expert consultation describes the same idea — total energy expenditure is BMR multiplied by a physical activity level (PAL).

Step 3 — daily target. Maintenance calories plus or minus the adjustment you set for your goal.

Step 4 — grams. Each macronutrient's share of the target is converted to grams with the Atwater general factors: 4 kcal per gram for protein and carbohydrate, 9 kcal per gram for fat. So grams = target kcal × percentage ÷ kcal per gram.

FAQ

How are the grams worked out?
Take your daily calorie target, multiply by each macro's percentage, then divide by the energy in one gram: 4 kcal for protein, 4 kcal for carbohydrate and 9 kcal for fat. These are the rounded Atwater general factors used in food-composition work — the FAO's technical report gives the more precise values as 16.7, 16.7 and 37.4 kJ/g. On a 2,000 kcal target, a 20/50/30 split gives 100 g protein, 250 g carbohydrate and 67 g fat.
What are the AMDR ranges the result mentions?
The Acceptable Macronutrient Distribution Ranges come from the US National Academies' Dietary Reference Intakes: 10–35% of calories from protein, 45–65% from carbohydrate and 20–35% from fat for adults. The same tables set the adult protein RDA at 0.8 g per kg of body weight per day, which is why the result also shows protein per kg. The calculator flags any split that falls outside these ranges for information only — a lower-carb split is outside them by design. Note that in November 2024 a National Academies committee recommended retiring the AMDR framework, saying the way the ranges were derived no longer meets current evidence standards; the ranges remain widely quoted, so they are shown here as a reference point rather than a rule.
Is this a diet plan?
No. It is an arithmetic estimate built on a population-average equation and a percentage split you choose; it knows nothing about your health, medication, training or medical history. For a general sense of scale, the NHS Eatwell Guide says women need around 2,000 kcal a day and men around 2,500 on average. A registered dietitian or your GP can turn an estimate like this into a plan that is actually right for you.

Sources

Figures used: Mifflin-St Jeor BMR equation (10 × kg + 6.25 × cm − 5 × age, +5 men / −161 women); Atwater general factors 4, 4 and 9 kcal/g; AMDR 10–35% protein, 45–65% carbohydrate, 20–35% fat; adult protein RDA 0.8 g/kg/day. The activity multipliers (1.2–1.9) and the default ±500 kcal/day goal adjustment are conventional calculator settings, not figures from these sources — FAO/WHO/UNU classify adult physical activity levels as 1.40–1.69 (sedentary or light), 1.70–1.99 (active or moderately active) and 2.00–2.40 (vigorous), so the lowest settings here are more conservative than that framework. Estimate only.