Calories are the energy in food. Estimating calories can help to prevent overeating and gaining weight.
What are calories?
Just like gasoline is fuel for your car, calories give your cells energy to function. If you were to overfill your gas tank, gasoline would spill all over the ground.
In the body, overfilling with calories will cause that excess fuel to be stored in fat cells, regardless of what type of food you eat.
How many calories do you need? Find out here.
Calories are Energy
The major energy sources in food are carbohydrates, proteins, fats, and alcohol. These provide different amounts of energy:
- 1 gram of carbohydrates = 4 calories
- 1 gram of protein = 4 calories
- 1 gram of fat = 9 calories
- 1 gram of alcohol = 7 calories
However, most of us do not weigh our foods, and most food is a combination of carbs, protein, and fat.
Calories in Common Foods
Instead of doing math, check out labels and menus to get an idea of how many calories are in a food. Here are examples:
How to interpret nutrition labels
Calories are listed on labels, BUT be aware that the serving size on the label and the amount eaten may differ. Example:
Suppose you ate 3 ounces of this product. How many calories did you eat?
1 serving = 1 ounce = 130 calories.
3 ounces = 3 servings = 390 calories
Note, if a nutrient is 10% or more, it is considered high.
Thus, if you ate 3 servings, you consumed 18% of your sodium and fat in this example, which is a lot from this one food!
Checking labels can help you estimate how many calories are in foods to stay within your body’s needs.
Eating more calories than you need will cause weight gain.
Calculate calories without labels
Nutrition labels may not always be available. However, estimating calories can be easily done.
- First, estimate the volume of food on your plate.
- Second, compare it to the official “standard serving size” used by the food industry.
- Third, do simple addition.
STEP 1 Estimate the amount of food on your plate (Portion)
Step 1 Portion
Portion is how much food you have on your plate.
Do you know what half a cup looks like? What about an ounce?
1 cup ~ size of a fist or baseball
½ cup ~ size of one cupped hand or racket ball
1 Tablespoon ~ size of thumb or dice
1 tsp ~ size of the tip of your thumb
3 ounces of meat ~ deck of cards or the size of the palm of your hand
If you are unsure of how much of each food is on your plate, you can measure out foods and liquids in your own dishes to get a sense of volume, or you can estimate amounts by using your hand or common items as shown above.
Step 2 Compare your Portion to the Standard Serving Size
Because food comes in all shapes and sizes, and some foods are denser (more compact) than others, standard serving sizes are used to help compare foods equally.
We can estimate the standard serving in foods by this chart:
| 1 standard serving of starch/bread/fruit is equal to: 1 slice of bread (1 ounce) ½ cup of cooked rice, cooked pasta, cereal ½ cup of juice 1 small to medium fruit |
| 1 standard serving of very lean to lean meats/ proteins is equal to: 1 ounce of lean beef, chicken w/o skin, fish ¼ cup cottage cheese 3 egg whites |
| 1 standard serving of med to high fat meats/ proteins is equal to: 1 ounce ground beef, pork, sausage 1 ounce pork, chicken with skin, fried fish 1 ounce mozzarella cheese 1 egg 1 Tbsp peanut butter |
| 1 standard serving of milk is equal to 1 cup of milk. |
| 1 standard serving of non-starchy veggies (not potatoes, corn, peas, beans) equal to: 1 cup raw veggies ½ cup cooked veggies |
| 1 standard serving of fats/oils is equal to: 1 tsp margarine, mayo, butter, oil 1 Tbsp salad dressing 1 Tbsp nuts or seeds 2 whole walnuts 1 slice bacon 1/8 avocado |
To see more standard serving sizes of different foods, see links at the end of this article.
STEP 3 add up the calories for each type of food
Now that you have compared each type of food on your plate (portion) to the standard serving size, add up the calories from each food using the table below to get the meal’s total calories.
The table below shows the calories in 1 standard serving for each type of food.
| 1 Standard serving | Calories |
| starch/ bread/ fruit (15 g carbs, 0-3 g protein, trace fat) | 60 – 80 |
| very lean to lean meat/ proteins (7 g protein 0-3 g fat) | 35 – 55 |
| medium to high fat meat/ proteins (7 g protein, 5-8 g fat) | 75 – 100 |
| milk Skim (12 g carbs, 8 g protein, 0-3 g fat) Low-fat (12 g carbs, 8 g protein, 5 g fat) Whole (12 g carbs, 8 g protein, 8 g fat) | 90 120 150 |
| non-starchy veggies (5 g carbs, 2 g protein) | 25 |
| fats (oils, butter) (5 g fat) | 45 |
Putting it all together
Example 1 Pasta
Step 1 Estimate portion size. Pasta on your plate is about the size of 2 baseballs or about 2 cups.
Step 2 Compare your portion to the standard serving size. 1 standard serving of pasta= half a cup.
Your plate has 4 standard servings of starches.
Step 3 add up calories (see green chart above). One standard serving of starches = 60-80 calories.
- (4 x 60) = 240
- (4 x 80) = 320.
Total calories are between 240 to 320.
Example 2 Turkey and Cheese Sandwich
2 slices of bread = 2 standard servings = 2 x 60 calories = 120 calories
2 ounces low fat turkey = 2 standard servings of lean meat = 2 x 55 calories = 110 calories
1 slice of cheese (~1 ounce) = 1 standard serving of high fat protein = 75 calories
Total calories = 120 + 110 + 75 = 305
Last Example – What about mixed foods?
It may be simple to calculate calories for a bowl of rice, but many foods are a combination of many types of ingredients.
For example, lasagna and enchiladas have starch and cheese and possibly meat and veggies.
You must break down the meal into its components. Example:
Enchiladas:
2 tortillas (2 starches ~80 cal each)
1 ounce of cheese (1 high fat, ~75 cal)
1 ounce of ground meat (1 med fat, ~75 cal)
Total = 310 calories
Summary
Determining how much energy is in food (aka calories) can help you stay within your energy needs and prevent weight gain. Need to lose weight? Here’s how to lose weight naturally and successfully long-term.
The easiest way to estimate calories is to look at nutrition facts on labels and on menus in restaurants.
Another way to keep track of calories is to compare your plate’s portion size to the food industry’s standard serving size and add up the calories. It sounds hard, but it’s only 3 steps. Try it a few times, and it gets easier.
Additionally, many apps can estimate calories, but some are not very accurate. To find out if an app is accurate, you can compare it to the official USDA food database. Then decide on one that you will actually use to get good at estimating how many calories you eat.
For more information and to see more standard serving sizes of foods go to:
Or see the American Diabetes Association diabetic exchange list for a comprehensive list of foods.
Content presented here, although created by US Registered Dietitians and PhD-level Nutritional Biologists, is for informational purposes only and is not intended to be medical advice. Consult your health care provider before using any supplements or making dietary changes.