How to Convert Carbohydrate Percent to Grams
After decades of research, scientists are slowly settling into the consensus that there is no single "best" diet for every person; an individualized approach is best. As you work toward the healthiest diet for you, the acceptable macronutrient distribution ranges (AMDRs) from the government's most recent dietary guidelines make a handy tool for ensuring healthy balance between your carbohydrate intake and other macronutrients. There's just one catch: You'll need to convert the AMDR's percentages into grams.
A Look at the AMDRs
In the 2015-2020 dietary guidelines for Americans, released by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, they recommend the following balance between macronutrients:
- Protein: 5 to 35 percent, depending on age
- Carbohydrate: 45 to 65 percent
- Fat: 20 to 40 percent, depending on age
Making these percentage recommendations – also known as the acceptable macronutrient distribution ranges or AMDRs – makes it easy to scale the proportions to fit your daily calorie intake. But most nutrition labels list carbohydrate, fat and protein in terms of grams, so in order to translate your macronutrient percentages into grams, you'll need to do the following calculations.
Converting From Percentages to Grams
Before you can convert percentages into grams for carbohydrates or any other macronutrients, you need to know your daily calorie target. This typically ranges between 1,800 and 3,000 calories for adults, depending on your age, gender and activity level. For this example, imagine that you have a goal of eating 2,000 calories per day and have decided to aim for 50 percent of those calories to come from carbohydrates – well within the AMDRs.
Convert From Percent to Decimal
Divide your macronutrient percentage (in this case, 50 percent carbohydrates) by 100 to convert it to a decimal:
50 ÷ 100 = .5
Multiply by Daily Calorie Target
Multiply the result from Step 1 – your carbohydrate percentage, expressed as a decimal – by your daily calorie target:
2,000 calories × .5 = 1,000 calories
This tells you how many calories out of your daily target should be dedicated to carbohydrates. You're almost there, but since your answer is in calories instead of grams, you have one more adjustment to make.
Divide by Calories/Gram
Each gram of carbohydrates provides 4 calories. So, to get from calories to grams, divide the result from Step 2 by 4:
1,000 calories ÷ 4 calories/gram = 250 grams
So, if you want to consume 50 percent of a 2,000-calorie diet in carbohydrates, that works out to 250 grams of carbohydrates.
Calculating Other Macronutrients
The same process applies to converting percentages into grams for other macronutrients, with one caveat. Like carbohydrates, protein provides 4 calories of energy per gram. But fats provide 9 calories of energy per gram. So, if you're calculating fat percentages into grams, your final step will involve dividing by 9 calories/gram instead of 4 calories/gram.
- Caloric intake depends on your age, health, nutritional status and activity level, along with many other factors.
- Carbohydrate percentage requirements vary primarily with your activity level and the type of activity. Carbohydrates replenish glycogen, the stored form of sugar in your muscles and liver. Glycogen is a major source of energy during exercise. A sedentary individual can benefit from eating 30 percent of calories from carbs; a strength athlete should eat 40 to 50 percent carbs and endurance athletes can benefit from diets containing as much as 70 percent carbs, according to nutritionist Dr. John Berardi.
- Note that you will require fewer calories and therefore fewer grams of carbs on non-workout days.
- Consult with your doctor before making any major dietary changes.
Lisa is a retired personal trainer with more than 4,000 hours of hands-on experience working with a variety of clients, from sports teams to weight loss and post-rehab populations. She's also a professional writer. Published credits in the health field include Livestrong.com, Feel Rich, SheKnows, Precor.com, and the East Coast magazine Breathe.