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Free Macro Calculator
Turn a calorie number into grams of protein, carbohydrate, and fat you can actually shop for — with presets for balanced eating, high protein, low carb, keto, endurance, and muscle gain.
Short answer
Start from your daily calorie target, choose a percentage split across protein, carbohydrate, and fat, then convert each share into grams — protein and carbohydrate provide 4 calories per gram, fat provides 9. A common balanced split for fat loss is 30% protein, 40% carbohydrate, 30% fat, and most guidance puts protein between 1.6 and 2.2 g per kilogram of body weight.
Calories decide the direction of the scale. Macros decide what changes underneath it — whether the weight you lose is fat or muscle, whether you have energy to train, and whether you are hungry all afternoon.
A percentage split is a starting point, not a rule. The one number worth defending is protein; the balance between carbohydrate and fat is mostly a question of what you enjoy eating and can keep doing.
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Macro Calculator
Turn a calorie target into grams of protein, carbohydrate, and fat you can actually shop for and eat.
Enough protein to protect muscle in a deficit, enough carbohydrate to train on, and enough fat for hormones and satiety.
Protein check: 2.05 g per kg of body weight
That clears the 125–187 g a day commonly recommended while losing fat at your body weight.
Where the calories came from
Maintenance is about 2680 kcal (Mifflin-St Jeor, moderately active), and your goal adjusts that to 2130 kcal a day. Change the goal above and every gram figure updates.
Hitting macros is the hard part, not calculating them.
Sign up and SlimAI stores these targets, counts every logged meal against them in grams, and shows the ingredient-level breakdown when a plate lands off target.
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Macro targets are starting points from population guidelines, not prescriptions. Adjust against how you train, recover, and feel. Not medical or dietary advice.
Which Macro Split Fits Your Goal
The right split depends on what you are asking your body to do. These are sensible defaults rather than rules — the split you can follow beats the optimal split you abandon in ten days.
Protein high, then split the rest however you like eating
In a deficit, protein does two jobs: it protects lean mass so the weight you lose is fat, and it is the most filling macro per calorie. Aim for 1.6–2.4 g per kg of body weight — around 30–40% of calories for most people. The carbohydrate and fat balance after that is a preference question, not a physiology question, provided fat stays above roughly 0.5 g per kg for hormone function.
Carbohydrate carries the training, protein builds the tissue
In a surplus, protein of about 1.6–2.2 g per kg is enough — more does not build muscle faster. Carbohydrate deserves the largest share because it fuels the training volume that drives growth and helps recovery between sessions. A 30/45/25 split is a reliable default for a lean gaining phase.
Steady calories, protein held, everything else flexible
At maintenance, macros are what make body recomposition possible: enough protein and enough training to add lean mass while fat comes down, with scale weight roughly flat. Keep protein at 1.4–2.0 g per kg, and treat the rest as room to eat food you enjoy without the plan falling apart.
What Each Macro Actually Does
The three macronutrients are not interchangeable calories. They do structurally different jobs, and that is why the split matters even when the total does not change.
Protein supplies the amino acids used to repair and build tissue, including the muscle you are trying to keep while losing weight. It has the highest thermic effect of the three — a meaningful share of the calories in protein is spent digesting it — and it is consistently the most satiating macro per calorie. In a deficit it is the one target worth protecting above all others.
Carbohydrate is the body’s preferred fuel for moderate and high-intensity work. Stored as glycogen in muscle and liver, it is what makes hard sets and long sessions possible. Cutting it very low does not stop fat loss, but it usually blunts training performance for the first couple of weeks, and it takes water weight with it — which is why low-carb starts look dramatic on the scale.
Fat is not optional. It is required for hormone production, cell membranes, and the absorption of vitamins A, D, E, and K. Very low fat intakes over long periods are a genuinely bad idea; most guidance puts the floor somewhere around 0.5 g per kilogram of body weight per day.
Protein — 4 kcal/g
Repairs and builds tissue, protects lean mass in a deficit, and keeps you full longest per calorie.
Carbohydrate — 4 kcal/g
Fuels moderate-to-hard training and refills glycogen. Carries water with it, which is why cutting it shows fast on the scale.
Fat — 9 kcal/g
Hormone production and fat-soluble vitamin absorption. More than twice the calories per gram, so small measuring errors cost more.
Fibre and alcohol
Fibre is a carbohydrate your body largely does not absorb; alcohol supplies 7 kcal per gram and belongs to none of the three.
Working out macros takes a minute. Hitting them takes an app.
SlimAI counts protein, carbohydrate, and fat in grams on every meal you log, and shows the ingredient-level breakdown when a plate lands off target.
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Why Percentage Splits Break Down at the Edges
Percentages are convenient and slightly dishonest. A "30% protein" target moves in grams every time your calorie intake moves — at 1,800 kcal it is 135 g, at 2,600 kcal it is 195 g. Your body did not change its protein requirement between those two days.
That is why protein is better anchored to body weight than to a share of calories. Grams per kilogram stays stable whether you are dieting, maintaining, or on a rest day when you eat less.
The same problem is sharper on keto. A 5% carbohydrate share sounds precise until intake shifts: at 1,800 kcal it is about 22 g, at 2,600 kcal it is closer to 33 g. Ketogenic eating is run as a hard gram ceiling for a reason — the threshold that matters is absolute, not proportional. This calculator shows both the percentage and the grams for exactly that reason.
Hitting Macros in Real Life
The gap between knowing your macros and hitting them is where most plans quietly die. Nothing about the arithmetic is hard; keeping score across every plate for weeks is.
A few things make it survivable. Build meals around a protein source first and fill in the rest — protein is the target you are most likely to miss and the one that matters most. Repeat meals you have already worked out instead of solving a new puzzle every day. Weigh the calorie-dense things, because a 20 g error in oil is 180 calories while a 20 g error in broccoli is about 7.
And decide up front how precise you are going to be. Landing within about 10 g of each target is well within the accuracy of any nutrition database. Chasing exact numbers is effort spent on precision the underlying data cannot support.
Protein first, then fill the gaps
Decide the protein source for each meal before anything else. Carbohydrate and fat are easier to adjust after the fact.
Repeat what already works
Three or four known breakfasts and lunches remove most of the daily decision-making.
Weigh what is calorie-dense
Oils, nuts, nut butters, and cheese carry the largest cost per gram of estimation error.
Aim for the week, not the day
A day that lands 15 g off protein means nothing. A week that lands consistently short does.
From a Calculated Split to a Tracked One
This page gives you three numbers. The work is everything after that — knowing what was on the plate you just ate and what it did to those numbers.
SlimAI Calorie Tracker is built around that step. Custom calorie goals let you set gram-level protein, carbohydrate, and fat targets rather than only percentage splits, which is what makes keto ceilings and athlete-style targets expressible in the first place. Log a meal by photo, voice, text, barcode, nutrition label, or search, and every macro updates against those targets in real time.
When a meal comes back higher in one macro than you expected, the food detail screen shows the ingredient-level breakdown — each ingredient with its weight and its own calorie and macro contribution — so you can see which component did it. Ingredients are editable, and your correction always overrides the AI. The serving stepper recalculates every macro before you commit, and suggests the exact fractional serving that still fits what is left of the day.
Because your targets live in your profile, they follow you. Change your goal, your weight, or your preferred diet, and the numbers move with you instead of needing to be recalculated on a website.
Common Macro Splits and Who They Suit
Every split below sums to 100% of calories. Protein is listed first, then carbohydrate, then fat. Use these as starting points and adjust based on training, appetite, and how you feel after two weeks.
| Split | Protein / Carbs / Fat | Best suited to |
|---|---|---|
| Balanced | 30% / 40% / 30% | General fat loss and everyday eating — the safest default |
| High protein | 40% / 35% / 25% | Fat loss while lifting, or anyone who gets hungry early in a deficit |
| Low carb | 35% / 20% / 45% | People who feel better on fewer carbohydrates and train at lower intensity |
| Keto | 25% / 5% / 70% | Ketogenic eating — but run the carb figure as a gram ceiling, not a percentage |
| High carb / endurance | 25% / 55% / 20% | Endurance athletes and anyone with high weekly training volume |
| Muscle gain | 30% / 45% / 25% | Building muscle in a calorie surplus with progressive resistance training |
Protein guidance of 1.6–2.2 g per kg for training individuals reflects widely cited position stands from sports nutrition bodies. Individual needs vary; these are not prescriptions.
How to Calculate Your Macros
Four steps. The calculator above does all of them, but the arithmetic is worth understanding so you can adjust without starting over.
- 1
Start with a calorie target
Use your TDEE, adjusted for your goal — roughly 550 kcal below maintenance for 0.5 kg a week of loss, or 250–350 kcal above for a lean gain. If you do not have that number yet, work it out with the TDEE calculator first.
- 2
Set protein from body weight, not percentages
Multiply your body weight in kilograms by 1.6–2.4 g while losing fat, or 1.6–2.2 g while gaining. A 78 kg person aiming for 2.0 g/kg needs about 156 g of protein a day, which is 624 calories.
- 3
Set a fat floor, then give the rest to carbohydrate
Keep fat at or above roughly 0.5 g per kg of body weight for hormone function — about 39 g for a 78 kg person, though most splits land well above that. Whatever calories remain after protein and fat go to carbohydrate.
- 4
Convert everything to grams
Divide protein and carbohydrate calories by 4, and fat calories by 9. At 2,000 kcal on a 30/40/30 split: 600 ÷ 4 = 150 g protein, 800 ÷ 4 = 200 g carbohydrate, 600 ÷ 9 = 67 g fat.
- 5
Track for two weeks, then adjust one thing
If weight is moving as planned but you are constantly hungry, shift calories from fat to protein. If training feels flat, move some to carbohydrate. Change one variable at a time or you will not know what worked.
The Formulas Behind This Calculator
All computed in your browser. Nothing is uploaded and nothing is stored between visits.
Calories per gram
protein = 4 kcal/g · carbohydrate = 4 kcal/g · fat = 9 kcal/gThe Atwater factors used by every nutrition database. Alcohol, not a macro target here, is 7 kcal/g.
Grams from a percentage split
grams = (calories × share%) / kcalPerGramCustom splits are normalised to 100% before conversion, so the three inputs do not have to add up exactly.
Protein per kilogram
proteinPerKg = proteinGrams / weight(kg)Checked against 1.6–2.4 g/kg while losing, 1.4–2.0 while maintaining, and 1.6–2.2 while gaining.
Per-meal targets
perMeal = dailyGrams / mealsPerDayAn even split across three or four meals. Real days are lumpier; the daily total is what matters.
Sources and method
- Atwater general factors — The 4/4/9 kcal-per-gram conversions for protein, carbohydrate, and fat used by nutrition labelling worldwide.
- International Society of Sports Nutrition — protein position stand — Protein intakes of roughly 1.4–2.0 g/kg and higher during energy restriction for individuals engaged in resistance training.
- Helms E, et al. — energy-restricted protein recommendations — Evidence supporting higher protein intakes (approximately 2.3–3.1 g/kg of lean mass) for retaining lean mass in a deficit.
- Institute of Medicine — acceptable macronutrient distribution ranges — Population-level ranges of 10–35% protein, 45–65% carbohydrate, and 20–35% fat, which the presets here sit around or deliberately outside.
FAQ
Still Wondering About SlimAI
Start with your daily calorie target, pick a percentage split across protein, carbohydrate, and fat, then divide each macro’s calories by its energy density — 4 kcal per gram for protein and carbohydrate, 9 for fat. At 2,000 calories on a 30/40/30 split that is 150 g protein, 200 g carbohydrate, and 67 g fat.
There is no single best split, because calories drive weight change and macros drive body composition. A 30–40% protein share works well for most people because protein protects lean mass in a deficit and is the most filling macro per calorie. Beyond that, choose the carbohydrate-to-fat balance you can actually stick to.
Most sports nutrition guidance puts it between 1.6 and 2.2 g per kilogram of body weight for people who train, rising toward 2.4 g/kg during a calorie deficit to protect lean mass. For a 78 kg person that is roughly 125–170 g a day. Sedentary adults need less, but higher protein still helps with fullness while dieting.
No — they answer different questions. Calories determine whether your weight goes up, down, or holds. Macros determine what that change is made of, how full you feel, and how well you train. Get calories right first, then use macros to make the result the one you wanted.
Total carbohydrate is the standard on nutrition labels in most countries. Net carbs subtract fibre and, in some regions, sugar alcohols. It mainly matters on ketogenic diets, where the carbohydrate ceiling is tight enough for the difference to be significant. Pick one convention and stay with it, since mixing the two makes your own data incomparable.
In SlimAI, yes. Custom calorie goals let you set your own daily calorie target and gram-level protein, carbohydrate, and fat targets rather than only percentage splits. That matters on keto, where the carbohydrate ceiling is an absolute number, and for athletes and coaches working to prescribed gram targets.
Within about 10 grams of each target is close enough — that is well inside the margin of error of any food database. Consistency across the week matters far more than precision on any single day.
Yes. Every food logged in SlimAI Calorie Tracker shows calories and macro grams with their percentage split, counted against your daily targets. The food detail screen breaks a meal down ingredient by ingredient with each one’s own macro contribution, ingredients are editable, and the serving stepper recalculates every macro before you save.
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