| Course | NS105 Fundamentals of Nutrition |
|---|---|
| Unit | Unit 3 |
| Paper type | Energy calculation set |
| Length | About 970 words, 6 pages double-spaced |
| Format | APA 7 student paper |
| School | Purdue University Global |
| Program | BS in Nutrition Science |
| Updated | October 2026 |
Free sample paper for NS105 Unit 3
Grams to Kilocalories to Percentages, Every Step Shown: A Unit 3 Energy Calculation Set Worked Through Five Problems
[Student Name]
Purdue University Global
NS105: Fundamentals of Nutrition
Unit 3 Energy Calculation Set
[Instructor Name]
[Date]
The foods and labels in the problems are composite; the energy factors and reference ranges cited are real.
The Energy Factors
All five problems use the general energy factors derived by Atwater and still used for food labeling and teaching: 4 kilocalories per gram of carbohydrate, 4 per gram of protein, 9 per gram of fat and 7 per gram of alcohol (Merrill & Watt, 1973). These are averages; actual values vary slightly by food. Fiber contributes less energy than digestible carbohydrate, which is one reason label calories may not match a calculation exactly.
Percentages of energy are always calculated from kilocalories, never from grams, because fat supplies more than twice the energy per gram of carbohydrate or protein. The results are compared with the Acceptable Macronutrient Distribution Ranges for adults: 45 to 65 percent of energy from carbohydrate, 20 to 35 percent from fat and 10 to 35 percent from protein (Institute of Medicine, 2005).
Problem 1: A Granola Bar
A granola bar contains 29 grams of carbohydrate, 3 grams of protein and 7 grams of fat. Find its energy and the percentage from each macronutrient.
Carbohydrate: 29 grams times 4 equals 116 kilocalories. Protein: 3 grams times 4 equals 12 kilocalories. Fat: 7 grams times 9 equals 63 kilocalories. Total: 116 plus 12 plus 63 equals 191 kilocalories.
Percentages: carbohydrate 116 divided by 191 equals 60.7 percent; protein 12 divided by 191 equals 6.3 percent; fat 63 divided by 191 equals 33.0 percent. Check: 60.7 plus 6.3 plus 33.0 equals 100.0.
The bar's label says 190 kilocalories, close to the calculated 191. Its protein share is low, but a single snack does not have to fall within the adult ranges; the ranges apply to a whole day's intake.
Problem 2: A Lunch
A lunch contains 68 grams of carbohydrate, 32 grams of protein and 21 grams of fat. Find its energy and percentages.
Carbohydrate: 68 times 4 equals 272 kilocalories. Protein: 32 times 4 equals 128 kilocalories. Fat: 21 times 9 equals 189 kilocalories. Total: 272 plus 128 plus 189 equals 589 kilocalories.
Percentages: carbohydrate 46.2 percent, protein 21.7 percent, fat 32.1 percent. Check: 46.2 plus 21.7 plus 32.1 equals 100.0.
All three fall within the adult ranges, which shows that a balanced meal can mirror the ranges set for the whole day.
Problem 3: Working Backward From a Label
A yogurt cup lists 150 kilocalories, 6 grams of protein and 2.5 grams of fat. The carbohydrate line is smudged. Estimate the carbohydrate.
Protein: 6 times 4 equals 24 kilocalories. Fat: 2.5 times 9 equals 22.5 kilocalories. Energy remaining: 150 minus 24 minus 22.5 equals 103.5 kilocalories. Carbohydrate: 103.5 divided by 4 equals about 26 grams.
The estimate assumes the label's total is exact. Because label values are rounded, the true carbohydrate could differ by a gram or two. Working backward is a useful check, not a substitute for the label.
Working a problem backward from the label's total shows how tightly the three numbers are linked: once energy, protein and fat are known, carbohydrate is no longer a free choice but the remainder.
Problem 4: A Drink With Alcohol
A 12-ounce beer contains 13 grams of carbohydrate, 2 grams of protein, no fat and 14 grams of alcohol. Find its energy and the percentage from alcohol.
Carbohydrate: 13 times 4 equals 52 kilocalories. Protein: 2 times 4 equals 8 kilocalories. Alcohol: 14 times 7 equals 98 kilocalories. Total: 52 plus 8 plus 98 equals 158 kilocalories.
Percentage from alcohol: 98 divided by 158 equals 62.0 percent. Carbohydrate 32.9 percent, protein 5.1 percent. Check: 62.0 plus 32.9 plus 5.1 equals 100.0.
Alcohol supplies more energy than the beer's carbohydrate. Because alcohol is not a nutrient, it has no acceptable range; its energy is counted in the day's total but not assigned to any of the three macronutrient ranges.
Problem 5: A Whole Day
A day's intake totals 255 grams of carbohydrate, 85 grams of protein and 78 grams of fat. Find the day's energy and check it against the ranges.
Carbohydrate: 255 times 4 equals 1,020 kilocalories. Protein: 85 times 4 equals 340 kilocalories. Fat: 78 times 9 equals 702 kilocalories. Total: 1,020 plus 340 plus 702 equals 2,062 kilocalories.
Percentages: carbohydrate 49.5 percent, protein 16.5 percent, fat 34.0 percent. Check: 49.5 plus 16.5 plus 34.0 equals 100.0.
All three fall within the ranges, though fat sits near the top of its range at 34 percent. A small shift, such as replacing a fried side dish with a baked one, would move it toward the middle.
Common Errors the Set Avoids
Three mistakes are frequent in energy calculations. The first is computing percentages from grams, which understates fat's share; in Problem 5, fat is only 18.7 percent of the grams but 34.0 percent of the energy. The second is rounding at each step, which can make totals fail to add to 100. The third is forgetting alcohol, which can make a day's macronutrient percentages look higher than they are. Carrying full figures through the working and checking each split against one hundred catches all three.
What the Numbers Do Not Show
These calculations describe the energy and macronutrient balance of foods and days. They say nothing about fiber, vitamins, minerals or the quality of the fats and carbohydrates. A day can fall neatly within every range and still be low in fiber or high in added sugars, which the national guidelines suggest keeping below 10 percent of energy (U.S. Department of Agriculture & U.S. Department of Health and Human Services, 2020). Later units examine those separately.
References
Institute of Medicine. (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press. https://doi.org/10.17226/10490
Merrill, A. L., & Watt, B. K. (1973). Energy value of foods: Basis and derivation (Agriculture Handbook No. 74). U.S. Department of Agriculture.
U.S. Department of Agriculture & U.S. Department of Health and Human Services. (2020). Dietary guidelines for Americans, 2020-2025 (9th ed.). https://www.dietaryguidelines.gov
NS105 Unit 3 instructions, in plain terms
The calculation unit asks students to compute the energy content of foods and diets and the share supplied by each macronutrient. Prompts usually provide grams or labels and expect kilocalories per macronutrient, total energy and percentages, often compared with the acceptable ranges. Show each multiplication, using 4 kilocalories per gram for carbohydrate and protein, 9 for fat and 7 for alcohol. Always calculate percentages from kilocalories, not grams. Carry full figures and round only at the end. Check that percentages add to one hundred. Explain small differences from label totals. Apply the adult ranges only to whole days, not single foods. Note what energy calculations cannot show. Four pages of worked problems is common.
How the NS 105 Unit 3 example is put together
An opening section gives the energy factors and the adult ranges, with sources. Problem one works a granola bar from grams to a 191-kilocalorie total and percentage split. Problem two shows a balanced lunch falling within every range. Problem three works backward from a yogurt label to estimate missing carbohydrate, and the highlighted sentence explains what that teaches. Problem four shows alcohol supplying most of a beer's energy. Problem five calculates a whole day and finds fat near the top of its range. A section names three common errors, including figuring percentages from grams, and a closing section notes what the numbers leave out. Every percentage split in the set closes by adding back to one hundred.
Where the points sit in the NS105 Unit 3 rubric
NS105 calculation rubrics give most of their points to correct arithmetic and correct method: the right energy factors, percentages from kilocalories and totals that check. Showing every step earns substantial credit, since graders need to see where an error occurs. Interpretation is scored separately, rewarding students who compare results with the acceptable ranges appropriately and explain label discrepancies. Recognizing alcohol as an energy source outside the ranges adds to accuracy. Clear layout and cited factors and ranges complete the rubric. A set that reports answers without working, or that calculates percentages from grams, will generally lose points even when some answers happen to be close. A short note on why a calculated total differs from a label, such as rounding or fiber's lower energy value, is often credited.
NS105 Unit 3 help: mistakes that cost points
Figuring percentages from grams, the slip seen most often here, badly understates fat. Another is rounding at every step, so the percentages fail to add to one hundred. Students sometimes apply the daily ranges to a single snack and call it unbalanced. Alcohol is often forgotten in drink problems. Working backward from a label is rarely attempted, though it shows real understanding. Differences from label totals are sometimes treated as errors rather than rounding. If your problem set has labels or grams you are unsure how to handle, send the figures, and a writer can walk through each calculation with every step shown.
Get an NS105 Unit 3 example written to your instructions
Attach the Unit 3 problems exactly as they were set, food values and all, along with the instructions and rubric. Each problem comes back worked on those numbers in the same given-method-check layout, delivered in 24-48h. A first custom sample costs nothing, and any rounding convention your instructor names is followed. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.
More NS105 papers and BS in Nutrition Science samples
- NS105 Unit 1: Nutrient Definition Post
- NS105 Unit 2: Digestion Summary
- NS105 Unit 4: Carbohydrate Profile
- NS105 Unit 5: Fat and Protein Comparison
- NS105 Unit 6: Seminar Reflection
- NS105 Unit 7: Three Day Food Record
- NS105 Unit 8: Nutrient Density Comparison
- NS105 Unit 9: Dietary Guidance Analysis
- NS105 Unit 10: Nutrition Case Summary
NS105 Unit 3 questions, answered
Should percentages come from grams or from kilocalories?
Always from kilocalories. Fat supplies more than twice the energy per gram of carbohydrate or protein, so a percentage built on grams understates fat's share of the day badly. Convert each nutrient to kilocalories first, total them, then divide each by the total. Your grader will likely recompute at least one of these, so show the division.
What if my totals do not match the label?
Small gaps are normal. Labels round their figures, some count fiber at a lower energy value, and the grams listed are themselves rounded. Report your computed total, state the label's figure beside it, and explain the difference in a sentence. A large gap is usually a conversion error worth checking before you submit.
Do I round at each step or only at the end?
Carry full figures through the working and round the final answers, unless your instructions say otherwise. Rounding early compounds small errors, and across a whole day it can shift a percentage by a point or more. Many sections state a rule for this in the prompt; if yours does, follow it exactly, even where it differs from this sample.
Where can I find a free NS105 Unit 3 sample paper?
This page holds a complete Unit 3 energy calculation set with five worked problems, every step shown and percentages checked, plus margin notes and APA references.
Why calculate percentages from kilocalories instead of grams?
Fat supplies 9 kilocalories per gram, more than twice carbohydrate or protein, so a percentage based on grams understates fat's share of energy. In the whole-day problem, fat is about 19 percent of grams but 34 percent of energy.