Free Macro Calculator — Protein, Carbs & Fat Grams (AMDR-Based) (2026)
Get your daily protein, carb, and fat grams from your TDEE across three splits — anchored to the Institute of Medicine AMDRs, with the ranges shown instead of hidden. Free, no signup.
Macros are your calories with a job description: protein for tissue, carbohydrate for fuel, fat for hormones and absorption. Enter five details and get gram targets across three splits — each positioned against the Institute of Medicine's acceptable ranges, not invented ratios.
How the splits are built
The Institute of Medicine's Acceptable Macronutrient Distribution Ranges put protein at 10 to 35% of your calories, carbohydrate at 45 to 65%, and fat at 20 to 35%. The balanced split (20/50/30) sits inside all three ranges.
The higher-protein (30/40/30) and lower-carb (30/35/35) splits put carbohydrate below the 45% floor, and their cards are marked. Both are popular, and in both, protein and fat stay inside their ranges. Grams use 4 calories per gram of protein or carbs and 9 per gram of fat.
Which split should you pick?
Adherence beats optimization: the best split is the one whose meals you'll actually keep eating. Protein is the macro with the strongest evidence for being deliberate — it preserves lean mass in a deficit and is the most satiating per calorie.
Carbs and fat are largely an energy-preference trade within the ranges. Athletes with high training volume usually feel better toward the carb ceiling; people who satiate on fat often prefer the other direction. Both work at equal calories.
Formula & sources
Resting calories (Mifflin-St Jeor BMR)
W = weight in kg, H = height in cm, A = age in years. Result in kcal/day.
Daily calories (TDEE)
The calories you burn in a day at your activity level. The grams below are worked out from this number.
Grams per macronutrient
The 4/4/9 Atwater factors. Percentages are of total daily energy.
Acceptable Macronutrient Distribution Ranges (AMDR)
IOM reference ranges, as % of energy.
| Macronutrient | % of energy |
|---|---|
| Protein | 10–35% |
| Carbohydrate | 45–65% |
| Fat | 20–35% |
Sources
- Mifflin MD, St Jeor ST, et al. (1990) A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241–247.
- Activity-factor scale The conventional activity multipliers used with the Harris-Benedict and Mifflin-St Jeor equations: 1.2 sedentary, 1.55 moderately active, 1.725 active, 1.9 very active. A widely used convention, not taken from a single study.
- Institute of Medicine (2005) Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids — Atwater factors and the AMDRs.
Macro questions, answered
What macros should I eat to lose weight?
Weight change is set by calories; macros set how the change feels and what it's made of. In a deficit, prioritize the protein end of the ranges (25–30% of energy) to protect muscle and manage hunger, then split the remainder between carbs and fat by preference.
How many grams of protein, carbs, and fat do I need?
This page shows your exact grams for each split at your calories. As a guide, the balanced split comes to 80 to 120 g of protein a day when maintenance is 1,600 to 2,400 calories.
Are these splits inside official guidelines?
Only the balanced split. Higher-protein and lower-carb put carbohydrate below the 45% floor, and their cards are marked. In both, protein and fat stay inside their ranges.
Do I need to hit macros exactly?
No. Daily ±10 g noise is irrelevant. Weekly averages near the targets — with protein the one you track most closely — deliver everything the precision theater does, with far less burnout.
Why grams instead of percentages?
You can't eat a percentage. Grams map to food labels and portions; that's also why the next step here is a plate: the MyPlate Plan converts the same calories into food groups you can actually shop for.
Do these macros change if I'm cutting or bulking?
The percentages can stay; the calories change. Set your target with the calorie-deficit calculator (or add a modest surplus), then apply the same split to that number — protein in absolute grams should stay high while cutting.