Key takeaways
- Macros are set in a fixed order: calories, protein, fat, then carbohydrate takes whatever is left.
- Protein is the only macro with a hard target — 1.6–2.2 g per kg of body weight when you are losing fat or building muscle.
- Fat has a floor, not a target: 0.6 g per kg minimum, and 20–35% of calories is the accepted range.
- A 2,000 calorie day on a balanced 30/40/30 split is 150 g protein, 200 g carbohydrate, 67 g fat.
- Percentages break at the extremes. Anchor protein and fat to body weight in kilograms, and treat the split as a starting shape.
Calculating macros means splitting a daily calorie target into grams of protein, carbohydrate and fat. Do it in four steps: set calories from your TDEE and your goal, set protein at 1.6–2.2 g per kg of body weight, set fat at 20–35% of calories, then give every remaining calorie to carbohydrate. Protein and carbohydrate supply 4 calories per gram and fat supplies 9, which is the only arithmetic involved.
What are macros, and why set them after calories?
Macronutrients are the three things in food that carry energy: protein, carbohydrate and fat. Everything else you eat — vitamins, minerals, water, fiber — matters for health but does not contribute meaningfully to your calorie total. That is why a macro split is not a separate diet plan. It is a decision about how to spend a budget you have already set.
The order matters because the two decisions do different jobs. Calories decide whether your weight moves. Macros decide what the weight is made of and how the diet feels while you are on it. Two people eating 2,000 calories with very different splits will see similar changes on the scale, but the one eating more protein typically holds onto more muscle and reports less hunger. Set the budget first, then divide it.
4 kcal
Per gram of protein
Same as carbohydrate — which is why grams and calories reconcile cleanly
4 kcal
Per gram of carbohydrate
Fiber is counted here, though much of it is not absorbed as energy
9 kcal
Per gram of fat
More than twice as dense, which is why fat portions are so easy to misjudge
Step 1: What should your calorie target be?
Your calorie target is your Total Daily Energy Expenditure adjusted for your goal — roughly 20% below TDEE to lose fat, 10% above to build muscle, and at TDEE to maintain. TDEE itself comes from the Mifflin-St Jeor equation multiplied by an activity factor between 1.2 and 1.9, which is what the 2BIB TDEE calculator runs.
If you want the whole derivation, including why a percentage deficit beats a flat 500 calories, that is covered in how many calories you should eat to lose weight. For the purposes of this post, assume you arrive here with a single number: a daily calorie target.
Step 2: How much protein should you set first?
Protein goes first because it is the only macro with a genuine requirement attached to your goal. The working range is 1.6–2.2 g per kg of body weight per day for anyone in a calorie deficit or training to add muscle, and 1.2–1.8 g per kg for general health at maintenance. A lean person in a steep deficit who lifts several times a week can justify up to 2.4 g per kg; above that there is no measured additional benefit.
| Body weight | General health (1.2–1.8 g/kg) | Fat loss or muscle gain (1.6–2.2 g/kg) |
|---|---|---|
| 55 kg / 121 lb | 66–99 g | 88–121 g |
| 70 kg / 154 lb | 84–126 g | 112–154 g |
| 85 kg / 187 lb | 102–153 g | 136–187 g |
| 100 kg / 220 lb | 120–180 g | 160–220 g |
Use current body weight unless you are carrying a lot of excess fat, in which case a target body weight or lean mass estimate gives a more sensible number.
The full reasoning behind those ranges, including how to split protein across meals and what happens above the top end, is in how much protein per day.
Step 3: How much fat before carbs get the rest?
Fat is set as a floor rather than a target. The practical minimum is 0.6 g per kg of body weight, and the accepted range for adults is 20–35% of total calories. Fat below the floor is not a faster way to lose weight; it is a way to run short on fat-soluble vitamins and to make food less satisfying, which tends to end the diet early.
Anywhere inside 20–35% is defensible, so this is the macro to set by preference. People who like larger evening meals and feel steadier on fewer carbohydrates land near 35%. People who train hard and need carbohydrate to fuel it land near 20–25%. Whatever is left after protein and fat becomes your carbohydrate target, which is simply total calories minus protein calories minus fat calories, divided by 4.
The arithmetic, once
Protein grams × 4 + fat grams × 9 = calories accounted for. Subtract that from your daily target, divide the remainder by 4, and you have carbohydrate grams. Every macro calculator on the internet is doing exactly this.
Which macro split should you choose?
A split is a shorthand for the same calculation expressed as percentages. Four shapes cover almost every reasonable goal, and these are the four the 2BIB macro calculator offers.
| Split | Protein / Carbs / Fat | Who it suits |
|---|---|---|
| Balanced | 30 / 40 / 30 | The default if you are unsure. Enough protein to hold muscle, enough carbohydrate to train on. |
| High protein | 40 / 35 / 25 | A calorie deficit, or a muscle-building phase. Maximises satiety and lean mass protection. |
| Lower carb | 35 / 25 / 40 | People who feel steadier on fewer carbohydrates, or who prefer fewer, larger meals. |
| Higher carb | 25 / 50 / 25 | Endurance training and physically demanding jobs, where carbohydrate is the working fuel. |
These percentages are starting shapes. Check the protein figure they produce against the g/kg table above and adjust if it lands outside the range.
What do the four splits look like at 2,000 calories?
Percentages are abstract; grams are what you log. Here is the same 2,000 calorie budget divided four ways.
| Split | Protein | Carbohydrate | Fat |
|---|---|---|---|
| Balanced 30/40/30 | 150 g | 200 g | 67 g |
| High protein 40/35/25 | 200 g | 175 g | 56 g |
| Lower carb 35/25/40 | 175 g | 125 g | 89 g |
| Higher carb 25/50/25 | 125 g | 250 g | 56 g |
At 2,000 calories, rounded to the nearest gram. Scale linearly for other targets: at 1,600 calories every figure is 20% smaller.
Notice the high-protein row. For a 70 kg person, 200 g of protein is 2.9 g per kg — well above the useful range, and 100 g of it is doing nothing that 120 g would not have done. That is the failure mode of percentage-only thinking, and it is why the g/kg check in step 2 is not optional.
Macros without the spreadsheet
2BIB sets your calorie and macro targets from your TDEE and goal, then counts protein, carbohydrate and fat automatically from a photo of your plate. Adjust the split any time and every target recalculates.
How should macros be spread across meals?
Protein is the macro worth distributing deliberately: aim for 0.4 g per kg of body weight per meal across three to four meals, which for most adults means 30–40 g each. Muscle protein synthesis responds to a per-meal dose rather than a daily pile, so 4 × 40 g does more for lean mass than 20 g, 20 g and 120 g at dinner, even though both total 160 g.
Carbohydrate and fat need no such structure. Place carbohydrate around training if you train hard, place fat wherever it makes meals enjoyable, and let the two trade against each other freely across the day.
A 150 g protein day
A 200 g protein day
Do you have to hit your macros exactly?
No, and trying to is the most common reason people stop tracking inside a month. Accuracy has a clear priority order, and the bottom of it does not matter much.
- 1Total calories — within about 100 of target. This is the only figure that determines weight change.
- 2Protein — within 5–10 g of target. This is what protects lean mass while the weight moves.
- 3Fiber — 25–38 g a day. Not a macro split decision, but it drives satiety more than the carbohydrate percentage does.
- 4The carbohydrate-to-fat ratio — whatever you actually enjoy. Swapping 20 g of carbohydrate for 9 g of fat changes nothing you can measure.
A week that averages correctly beats four perfect days and three abandoned ones. If your portion estimates are the weak link rather than your discipline, tracking calories without a food scale covers how to keep a log honest by eye.
When to check with a clinician first
These ranges describe healthy adults. If you have kidney disease, diabetes, are pregnant or breastfeeding, or are taking a GLP-1 medication, protein and carbohydrate targets may need to be set differently — talk to your doctor or a registered dietitian before making a large change.
When should you recalculate?
Macro targets follow calories, and calories follow body weight. Recalculate after every 5% of body weight lost or gained, after a meaningful change in training volume, and any time the weight trend stalls for three weeks or more.
- Weight changed by 5%. TDEE moved with it, so the deficit you set is no longer the deficit you are eating.
- Training changed. Adding or dropping three sessions a week shifts the activity multiplier a whole step.
- Three flat weeks. Usually a plateau rather than a broken formula — check logging accuracy before cutting calories again.
- The split is not being hit. If you miss protein every day, the target is wrong for how you eat. Lower it to a number you actually reach.
The short version
Calories from TDEE and goal. Protein at 1.6–2.2 g per kg. Fat at 20–35% of calories, never below 0.6 g per kg. Carbohydrate takes the remainder. Pick the split that matches how you like to eat, check the protein figure against your body weight, and then spend your attention on hitting calories and protein rather than on the third decimal place of a ratio.