Macro Calculator for Carbs, Protein and Fat
Use this macro calculator to turn the daily calories you already have, from your dietitian, doctor or own plan, into grams of carbohydrate, protein and fat.
Work out your macros in grams
Your numbers (example values shown; replace them with your own. The example is not a recommendation.)
Share of calories (adds up to 100%)
Grams eaten or planned per day
How the macro calculator works
The macro calculator turns a daily calorie amount and a percentage split into grams of carbohydrate, protein and fat. It uses the general Atwater factors: 4 kcal per gram of carbohydrate, 4 kcal per gram of protein and 9 kcal per gram of fat.
calories from a macro = daily calories × percentage ÷ 100
grams a day = calories from that macro ÷ kcal per gram
grams per meal = grams a day ÷ meals a day
The calorie figure has to come from you. It might be the number your dietitian or doctor gave you, the amount in a plan you follow, or what you have tracked yourself. The tool does not estimate calorie needs and does not suggest a split. It does the arithmetic exactly and shows how your split compares with a general reference range.
Worked example: 2,000 kcal at 50/20/30
Here 2,000 kcal a day is split into 50% carbohydrate, 20% protein and 30% fat, eaten over 3 meals. The numbers are an example, not a target.
| Macronutrient | Share | Calories | Grams a day | Per meal (3 meals) |
|---|---|---|---|---|
| Carbohydrate | 50% | 1,000 kcal | 250 g | 83.3 g |
| Protein | 20% | 400 kcal | 100 g | 33.3 g |
| Fat | 30% | 600 kcal | 66.7 g | 22.2 g |
Fat gives fewer grams than protein for more calories, because each gram carries 9 kcal rather than 4. Per-meal amounts are rounded to 0.1 g, so three meals of 22.2 g add up to 66.6 g rather than 66.7 g.
What do the 4, 4 and 9 mean?
They are the general Atwater factors, average energy values per gram that use a single figure for each nutrient whatever food it comes from. The FAO’s report on food energy gives them as 4 kcal per gram for protein and carbohydrate and 9 kcal per gram for fat. Because they are averages, a figure worked out this way can differ slightly from the energy of a particular food. The same report lists dietary fibre at about 2 kcal per gram and alcohol at about 7 kcal per gram; this tool does not count alcohol. Treat the results as close estimates for planning, not laboratory values.
Is my split within the reference ranges?
The macro calculator compares your split with the US Acceptable Macronutrient Distribution Ranges (AMDRs) for adults, published by the National Academies: 45–65% of calories from carbohydrate, 10–35% from protein and 20–35% from fat. A share outside its range is flagged so that you can see it, and nothing more.
These ranges are broad references for the general adult population, not personal targets, and they are not meant for children. A plan from a doctor or registered dietitian may sit outside them for good reasons. If you have diabetes, kidney disease or another health condition, take medicines that affect eating, or are pregnant or breastfeeding, ask a doctor or registered dietitian about your own split. For background on two popular eating patterns, see our high-protein fat loss diet plan and our article on the keto diet and brain clarity.
How do I turn grams into percentages?
Choose “Grams to calories and %” and enter the grams of carbohydrate, protein and fat for the day. The calculator multiplies each by its factor, adds them up and shows each macronutrient’s share of the total:
share = grams × kcal per gram ÷ total calories × 100
For example, 250 g of carbohydrate, 100 g of protein and 70 g of fat supply 1,000 + 400 + 630 = 2,030 kcal. That is 49.3% from carbohydrate, 19.7% from protein and 31% from fat. To find the grams in what you actually eat, the nutrition label portion calculator scales a food label to your portion.
Tips for using your numbers
- Grams of protein are not grams of food. A target of 100 g of protein means the protein across everything you eat in the day, not 100 g of chicken. Read each food’s label, or use the nutrition label portion calculator, to work out how much food that is.
- Meals do not have to be equal. The per-meal column divides the day evenly. If your plan puts more protein in one meal, work from the daily totals.
- Decimals keep the totals honest. They are there so the meals add up to the day; in the kitchen, whole grams are easier to weigh.
- Your numbers are saved in this browser, so your split is still there next time.
What this macro calculator cannot do
It does not work out how many calories you need, recommend a split or judge whether a diet suits you. It does not count alcohol, the exact energy of individual foods or any medical needs. Take questions about the numbers themselves to a doctor or registered dietitian. Within those limits, the macro calculator is a quick, exact way to turn a plan you already have into grams for every meal.
Sources for this calculator
- FAO, Food energy: methods of analysis and conversion factors, chapter 3 (general Atwater factors; energy of fibre and alcohol).
- National Academies: Rethinking the Acceptable Macronutrient Distribution Range for the 21st Century (adult AMDRs).
Frequently Asked Questions
Multiply your daily calories by the percentage for each macronutrient, then divide by its calories per gram: 4 for carbohydrate, 4 for protein and 9 for fat. For 2,000 kcal with 30% fat, 2,000 × 30 ÷ 100 = 600 kcal, and 600 ÷ 9 = 66.7 g of fat. The macro calculator does this for all three and divides the grams between your meals.
Fat holds more energy per gram than carbohydrate or protein. The general Atwater factors, described by the FAO, use 9 kcal per gram for fat and 4 kcal per gram for carbohydrate and protein. They are averages applied to all foods, so a specific food can differ slightly. The FAO lists alcohol at about 7 kcal per gram and dietary fibre at about 2 kcal per gram.
This tool does not recommend a split, because the right one depends on your health, medicines, activity, age and goals. As a general reference, the US ranges for adults are 45–65% of calories from carbohydrate, 10–35% from protein and 20–35% from fat. For a split that fits you, especially with diabetes, kidney disease or pregnancy, ask a doctor or registered dietitian.
The calculator does not estimate calorie needs. They depend on age, sex, body size, activity and health, and a doctor or registered dietitian can give you a figure that suits you. Once you have a daily calorie amount from them or from your own plan, enter it here (between 500 and 10,000 kcal) to turn it into grams.
They must add up to 100%, with up to 0.5 percentage points either way for rounding. A split of 33.3%, 33.3% and 33.3% adds up to 99.9% and is accepted; the calculator then tells you that the grams supply 1,998 kcal of a 2,000 kcal plan. A larger gap shows an error saying how many points to add or remove.