About the Macro Calculator
A free educational tool that splits a calorie intake into protein, carbs, and fat grams — with preset and custom ratios, an optional maintenance estimate, and a clear guide to each macronutrient.
What it is
The Macro Calculator is an educational reference tool that answers one question: given a calorie amount and a macro split, how many grams of protein, carbohydrates, and fat does that work out to? It is not a goal-based diet tool and does not generate a calorie target or a weight-change plan — those decisions belong with a qualified professional.
You provide the calories — either by entering a number directly, or by using the optional built-in maintenance estimate — and choose a macro ratio from the presets or enter your own custom percentages. The tool converts that split to grams using the established kcal-per-gram values (protein and carbs: 4 kcal/g, fat: 9 kcal/g) and shows the math clearly. Everything runs in your browser; no data is sent to a server or stored anywhere.
Key features
Preset & custom splits
Choose from three common macro ratios — Balanced (40C/30P/30F), Higher-Protein (30C/40P/30F), or Low-Carb (20C/35P/45F) — or enter any custom percentages that sum to 100%.
Grams with kcal math shown
Displays grams and kilocalories for each macronutrient, with the calculation note so you can see exactly how each figure was derived — no black-box outputs.
Stacked proportion bar
A colour-coded bar shows the visual proportions of carbs, protein, and fat in your split, with a legend showing each percentage at a glance.
Optional maintenance estimate
Enable the maintenance estimate to get a TDEE figure from your height, weight, age, sex, and activity — using the same Mifflin-St Jeor or Harris-Benedict formulas as the TDEE Calculator — and apply it to the macro split in one click.
The macronutrient basics
Carbohydrates — 4 kcal/g
The body's primary energy source. Digested into glucose for use by the brain, muscles, and organs. Found in grains, fruit, vegetables, legumes, and dairy.
Protein — 4 kcal/g
Essential for building and repairing muscle, enzymes, hormones, and body structures. Found in meat, fish, eggs, dairy, beans, and soy. Used for fuel only when carbohydrate and fat are insufficient.
Fat — 9 kcal/g
A concentrated energy source, also essential for fat-soluble vitamins (A, D, E, K), cell membranes, and hormones. Fat provides more than twice the energy per gram of carbs or protein.
What this tool does and doesn't do
It does: take a calorie input (manual or estimated), apply a chosen macro ratio, output grams of carbs, protein, and fat with the kcal-per-gram math visible, and explain what each macronutrient is.
It doesn't: prescribe a calorie target for weight loss or gain, include a goal selector or deficit/surplus pathway, set target weights, or produce any "cut/bulk plan". There are no aggressive-cut presets or very-low-calorie pathways — those decisions belong with a qualified professional.
Important: educational reference only
This tool is a general reference for understanding how macronutrients divide up a given calorie intake. It is not medical or dietary advice. Please consult a registered dietitian or physician before making any significant change to your diet, calorie intake, or nutrition — especially if you have any health condition, are pregnant, or are managing a medical issue. Individual needs vary, and only a qualified professional can give advice tailored to you.
If you ever find yourself preoccupied with restricting food or with your weight, please consider reaching out to a qualified professional for support.
Have questions? See the Macro Calculator FAQ.