Macro Calculator
Turn a calorie target into specific gram goals for protein, carbohydrates, and fat. Enter a calorie number you already know, or let the calculator estimate your daily energy needs from your age, sex, height, weight, activity level, and goal, then choose a macro split and see the grams, calories, per-meal targets, and an optional grocery cost.
Formula
Worked example
2,000 kcal balanced (40C/30P/30F): carbs 200 g, protein 150 g, fat ≈ 67 g.
How the Calculator Works
Each macronutrient carries a fixed caloric value: protein and carbohydrates each provide 4 kilocalories per gram, while fat provides 9 kilocalories per gram. The calculator allocates your daily calorie target across the three macronutrients by the percentage split you pick, then converts each share to grams using the appropriate caloric density. If you do not already have a calorie number, switch the calorie source to estimate it: the tool computes your basal metabolic rate (BMR) with the Mifflin-St Jeor or Katch-McArdle equation, multiplies by an activity factor to get total daily energy expenditure (TDEE), and adjusts for a weight loss or gain goal. The three gram targets you get can be tracked against food labels or a nutrition app.
Estimating Calories From Your Body Stats
When you choose to estimate calories, the Mifflin-St Jeor equation predicts BMR from your weight, height, age, and sex, and is the formula most dietitians use for healthy adults. The Katch-McArdle option instead uses your lean body mass, derived from a body fat percentage, and can be more accurate for lean or muscular people. BMR is multiplied by an activity factor from 1.2 for sedentary up to 1.9 for extra active to produce maintenance calories (TDEE). A goal then shifts that number: a deficit of 250, 500, or 1000 calories per day targets roughly a quarter, half, or one kilogram of loss per week, and matching surpluses target gain. Metric and imperial units are both supported.
Choosing a Macro Split
The calculator ships with several evidence-informed presets: a balanced 40/30/30 split, a higher-protein plan, low-carb, ketogenic, and high-carb. You can also pick the custom option and set your own carb, protein, and fat percentages, which the calculator normalises to 100% so the math always balances. To sanity-check the protein target, the result also shows protein in grams per kilogram of body weight, a common muscle-building range is 1.6 to 2.2 grams per kilogram. The split changes the gram outputs as much as the calorie total does, so it is worth trying a few and seeing which targets feel realistic for the foods you actually eat.
Per-Meal Targets and Grocery Cost
Beyond the daily totals, the calculator divides your macros across the number of meals you eat so you have a practical per-meal protein, carb, and fat target to aim for. Turn on the optional cost estimate and enter a rough price per 1000 calories of food to see an approximate daily and monthly grocery spend, useful for budgeting a meal plan. These breakdowns are planning aids: real meals rarely split perfectly evenly, and food prices vary widely by region and diet quality, so treat the figures as a starting framework rather than a fixed prescription.
Limitations to Keep in Mind
This calculator provides general informational output; it does not constitute personalised medical or nutrition advice. Calorie estimates from BMR equations carry an error of roughly plus or minus 10%, so use them as a starting point and adjust based on real-world weight change over two to three weeks. The tool does not account for micronutrient adequacy, food quality, meal timing, or individual health conditions such as diabetes, kidney disease, pregnancy, or disordered eating history, all of which can make a standard macro calculation inappropriate or even harmful without professional guidance. Caloric needs also change as body weight and activity shift, so revisit any macro plan periodically and consult a registered dietitian or qualified healthcare provider before making significant changes to your diet.
Common macro splits and when people use them
| Split | Carbs | Protein | Fat | Often used for |
|---|---|---|---|---|
| Balanced | 40% | 30% | 30% | General health, easy to follow |
| High-protein | 40% | 40% | 20% | Muscle gain, appetite control |
| Low-carb | 25% | 40% | 35% | Fat loss, blood sugar control |
| Keto | 5% | 25% | 70% | Ketogenic dieting |
| High-carb | 55% | 25% | 20% | Endurance training, high volume |
Carbs / protein / fat as a percent of total calories. Starting points, not prescriptions.
Frequently asked questions
Why do protein and carbs have different caloric values than fat?
Protein and carbohydrates each yield approximately 4 kilocalories per gram when metabolised, a figure derived from bomb calorimetry and digestibility corrections established in the Atwater general factors. Fat is chemically more energy-dense, providing approximately 9 kilocalories per gram because fatty acids contain a higher proportion of carbon-hydrogen bonds relative to oxygen. These values have been used in food labelling regulations in the United States and internationally for decades.
Is there an optimal macro ratio for weight loss or muscle gain?
Research does not support a single universally optimal ratio for either goal. For muscle gain, adequate protein intake, often cited in the range of 1.6 to 2.2 grams per kilogram of body weight per day in resistance-trained individuals, appears more important than the specific carbohydrate-to-fat split. For weight loss, total calorie deficit is the primary driver, though higher protein intakes are associated with greater satiety and lean mass preservation during a deficit. Individual response, food preferences, and adherence matter considerably.
Can I use this calculator if I follow a specific diet like keto or high-protein?
Yes, the calculator is ratio-agnostic. Pick a preset such as keto (5% carbs, 25% protein, 70% fat) or high-protein, or choose the custom option and enter any carb, protein, and fat percentages you like. The calculator normalises your numbers to 100% and the resulting gram figures are mathematically accurate for any ratio. Whether a particular ratio is appropriate for your health situation is a clinical question best answered in consultation with a healthcare professional.
Should I enter my own calories or let the calculator estimate them?
If you already track calories or have a target from a dietitian, enter it directly under the manual calorie source. If you do not, switch the source to estimate and the calculator will compute your maintenance calories from your age, sex, height, weight, and activity level using the Mifflin-St Jeor or Katch-McArdle equation, then apply your weight goal. Estimated calories are accurate to within about 10% for most people, so adjust after watching your weight trend for a couple of weeks.
How much protein per kilogram of body weight should I aim for?
For general health, dietary guidelines suggest at least 0.8 grams of protein per kilogram of body weight per day. People who train for strength or are dieting to preserve muscle commonly aim higher, in the range of 1.6 to 2.2 grams per kilogram. The calculator shows your protein target both in total grams and in grams per kilogram so you can check it against these benchmarks and adjust the macro split if needed.
Sources
- Dietary Guidelines for Americans 2020-2025, Acceptable Macronutrient Distribution Ranges (U.S. Department of Health and Human Services & USDA)
- Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (National Academies Press)