Macro Calculator (Grams of Carbs, Protein and Fat)

A macro calculator turns your daily calorie target into grams of the three macronutrients: carbohydrate, protein and fat. You give it your calories and a split, for example 50% carbs, 20% protein and 30% fat, and it converts each share into grams with 4, 4 and 9 calories per gram. It does not set your calories or tell you which split to follow.

Enter the calories you plan to eat in a day, pick a split from the list or choose Custom and type the percent for carbs and protein (fat gets the rest), and read your grams. The lines next to the result show how each share compares with the adult ranges in the Dietary Guidelines. Then log your food in grams and aim for those totals over the day.

Macronutrients are carbohydrate, protein and fat, the three nutrients your food supplies in gram amounts and that carry its calories: 4 calories per gram for carbohydrate and protein and 9 for fat. For adults the Dietary Guidelines for Americans give an acceptable range of shares of daily calories for each one.

Set your calorie target, choose a split and read your gram targets. Then log what you eat in grams: US Nutrition Facts labels list grams of total fat, total carbohydrate and protein per serving (21 CFR 101.9(c)), so weigh your portion and scale the label. Add up the day and compare it with your targets. Label amounts are rounded, so expect small differences.

It is the calories in a gram of each macronutrient: 4 for carbohydrate, 4 for protein and 9 for fat. US food labeling rules allow these general factors for the calories on a Nutrition Facts label (21 CFR 101.9(c)(1)). Multiply the grams of each by its factor and add them up to get calories, or go the other way: 800 calories of protein is 800 ÷ 4 = 200 g.

It splits your calories 40% carbohydrate, 40% protein and 20% fat. At 2,000 calories that is 200 g of carbs, 200 g of protein and about 44 g of fat. It is a rule of thumb, not part of the Dietary Guidelines: its carbohydrate share is below the adult range of 45 to 65% and its protein share is above the adult range of 10 to 35%.

Multiply your daily calories by the percentage to get the calories from that macro, then divide by its calories per gram: 4 for carbs and protein, 9 for fat. For 2,500 calories with 30% from protein: 2,500 × 0.30 = 750 calories, and 750 ÷ 4 = 187.5 g of protein. The calculator does this for all three macros at once.

For adults the Dietary Guidelines for Americans 2020 to 2025 list 45 to 65% of calories from carbohydrate, 10 to 35% from protein and 20 to 35% from fat. These Acceptable Macronutrient Distribution Ranges were set by the National Academies, and the Guidelines give different ones for children and teenagers. The Dietary Guidelines site now points to a newer edition.

Yes. Choose Custom in the split list, then type the percent of calories for carbs and protein. Fat gets the remainder, so the three shares always add up to 100%. If carbs and protein add up to more than 100%, the calculator asks you to lower one of them.

The list has seven example splits, written carbs / protein / fat: balanced (50/20/30), higher carb (60/15/25), moderate carb (40/30/30), 40/40/20, higher protein (35/35/30), lower carb (25/35/40) and keto, a very low carb split (5/20/75). Custom takes your own numbers. They are splits of calories, not complete diet plans.

Estimate it with the TDEE calculator, which finds your resting calories from age, height and weight and scales them by your activity level. It is an estimate: if your weight holds steady for a few weeks at a given intake, that intake is your maintenance level. Type that number in as your daily calories here.

Enter a calorie target meant for weight loss, then pick a split. The calculator turns whatever calories you type in into grams; it does not decide how much you should eat. For a target, choose one of the Lose options in the Goal list of the TDEE calculator, which take 250 to 1,000 calories a day off your estimated maintenance calories, and enter the result here. The Gain options work the same way if you want to gain weight. A very low target, or a split outside the adult ranges, is a decision for you and your doctor or registered dietitian.

No. The presets are example splits, not prescriptions, and several fall outside the adult ranges in the Dietary Guidelines. The right split depends on your health, medications, goals and preferences. If you have a medical condition, are pregnant or take medication, ask your doctor or a registered dietitian before you change how you eat.

Calories tell you how much energy you eat; macros also show what it is made of. At 2,000 calories, a protein share of 10% is 50 g and a share of 30% is 150 g, so the same calorie count can hide a 100 g difference in protein. The benefit of tracking macros is more control over that mix and a way to check it against the Dietary Guidelines ranges. Calories still matter.