How to Calculate Protein, Carbs and Fat Intake for Runners

Article Difficulty: Easy

🕗 10 minute read

This article is a guide to calculating your protein, carbohydrate, and fat requirements as a runner. It follows a step by step method of how to calculate your protein, carbohydrate and fat requirements for optimal performance, based on the most recent scientific literature in running and endurance performance. 

This is a manual step by step approach to calculating your daily macronutrient needs, however, we also have a free macronutrient calculator that does it all for you. I’ve written this article so you have a full understanding of how to do it as it’s useful for designing any kind of basic nutrition program for athletic performance. 

I’ve written a detailed blog explaining why runners need 1.8 grams of protein per kilogram of body mass per day, and this is the protein amount used in this guide. Fats are set at 20-30% of daily calorie intake, and the remainder of daily energy intake is made up of carbohydrates, as there is substantial literature supporting this range for optimal endurance performance. 

To calculate your daily macronutrient needs, you need to know the following

• Your body mass in kilograms or pounds
• Your daily energy requirements. This is the number of kcals you consume at maintenance — meaning, the amount of energy you take in without any change in body mass.

Step 1

Calculate Protein Needs

• Multiply 1.8 by your body mass in kilograms to calculate your daily protein intake in grams.
• If using pounds, multiply 0.82 by your body mass in pounds.

The value you recieve from this calculation is your daily grams of protein required.

You then need to multiply this value in grams by 4 to calculate your total daily protein intake in kilocalories. For each macronutrient—protein, fat, and carbohydrate, you need to record both the gram amount and the corresponding kcal value.

• A gram of protein = 4 kcals
• A gram of fat = 9 Kcals
• A gram of carbohydrate = 4 kcals

Step 2

Calculate Fat Needs

Select either 20%, 25%, or 30% of your daily energy intake as your fat target.

1. Multiply your total daily energy needs (in kcal) by the chosen percentage:
   Daily kcal × fat % = kcal from fat
2. Divide the result by 9 (since fat provides 9 kcal per gram):
   Kcal from fat ÷ 9 = grams of fat per day

Note that there's a range of acceptable fat values, 20-30%. You have the choice depending on your dietary preference. However, I recommend going on the higher end (25-30%) if you have a low daily energy expenditure (<1800 kcals) simply because 20% of <1800 kcals is only <380 kcals of fat which is low for most people. I personally choose the lower end (20%) to maximize the amount of carbohydrates I'm consuming. 

Step 3

Calculate Carbohydrate Needs

Fill in the remaining energy with carbohydrates.

To do this, subtract the kcals from protein and fat from your total daily energy needs:

Carbohydrate (kcals) = Total daily energy (kcals) − Protein (kcals) − Fat (kcals)

You will receive a value in kcals. Divide this value by 4 to get your carbohydrate in grams

Step 4

Calculate percentage amounts

You will now have both gram and kcal values for each macronutrient.

Sum the three kcal values to ensure they equal the total daily energy requirement you started with. If they don’t, double-check your calculations!

If you want to calculate the percentage of total energy from protein and carbohydrate (you already have fat), simply divide the kcals from the corresponding nutrient by your total daily energy intake:

Percentage = (Nutrient kcals ÷ Total daily kcals) × 100

Step 5

Totals

You now have everything you need for your daily macronutrient breakdown:

• Protein in grams, kcals, and as a percentage of daily intake
• Fat in grams, kcals, and as a percentage of daily intake
• Carbohydrate in grams, kcals, and as a percentage of daily intake

That’s it! Follow the steps above and you’ll have your daily macronutrient needs calculated for optimal running performance and recovery. The remainder of the article walks through a couple of real-life examples to help illustrate the calculations, along with a few additional factors worth considering.

Again, if you'd like a simple tool to calculate all of this for you, check out our free macronutrient calculator for runners.

Two real life examples (me and my wife)

Here I've included two real life examples, to help understand the process. The same step by step approach is used, but this time we're using actual values.

Example 1: Joe

Body mass: 140lbs
Maintenance calorie intake: 3200 Kcals

Step 1:

Protein

• 0.82 g × 140 lbs = 115 g protein per day
  (I’m using pounds, not kilograms.)
• 115 g × 4 kcal/g = 460 kcal from protein

Step 2:

Fat

• 20% of 3200 kcal = 640 kcal
• 640 kcal ÷ 9 kcal/g = 71 g fat

Step 3:

Carbohydrate

• Remaining kcals = 3200 − 460 (from protein) − 640 (from fat) = 2100 kcal
• 2100 kcal ÷ 4 kcal/g = 525 g carbohydrate

Step 4

Calculate percentage amounts

• Protein percentage of energy = (460 kcals / 3200 kcals) * 100 = 14%
• Fat percentage of energy = 20%
• Carbohydrate percentage of energy = (2100 kcals / 3200 kcals) * 100 = 66%

Step 5:

Totals

• Protein = 115 g, 460 kcals, 14% of daily energy
• Fat = 71 g, 640 kcals, 20% of daily energy
• Carbohydrate = 525 g, 2100 kcals, 66% of daily energy

Again, the percentage of daily energy is calculated by dividing the kcals from the nutrient by the total daily energy intake.

Example 2: Gillian

Body mass: 150lbs
Maintenance calorie intake: 2100 Kcals

Step 1:

Protein

• 0.82 g × 150 lbs = 123 g protein per day
  (I’m using pounds, not kilograms.)
• 123 g × 4 kcal/g = 492 kcal from protein

Step 2:

Fat

• 20% of 2100 kcal = 420 kcal
• 420 kcal ÷ 9 kcal/g = 47 g fat

Step 3:

Carbohydrate

• Remaining kcals = 2100 − 492 (from protein) − 410 (from fat) = 1188 kcal
• 1188 kcal ÷ 4 kcal/g = 297 g carbohydrate

Step 4

Calculate percentage amounts

• Protein percentage of energy = (460 kcals / 3200 kcals) * 100 = 23%
• Fat percentage of energy = 20%
• Carbohydrate percentage of energy = (2100 kcals / 3200 kcals) * 100 = 57%

Step 5:

Totals

• Protein = 123 g, 492 kcals, 23% of daily energy
• Fat = 47 g, 420 kcals, 20% of daily energy
• Carbohydrate = 297 g, 1188 kcals, 57% of daily energy

Comparing the examples

You can see from the two different examples (totals below) that, although we're using the same calculation method, we end up with very different outputs. That’s because, despite having similar body mass (140 lbs and 150 lbs), our daily energy needs are quite different—3200 kcals for me and 2100 kcals for my wife, which significantly impacts the fat and carbohydrate amounts.

Joe Totals

Body mass 140 lbs, daily energy expenditure 3200 kcals

• Protein = 115 g, 460 kcals, 14% of daily energy
• Fat = 71 g, 640 kcals, 20% of daily energy
• Carbohydrate = 525 g, 2100 kcals, 66% of daily energy

Gillian Totals

Body mass 150 lbs, daily energy expenditure 2100 kcals

• Protein = 123 g, 492 kcals, 23% of daily energy
• Fat = 47 g, 420 kcals, 20% of daily energy
• Carbohydrate = 297 g, 1188 kcals, 57% of daily energy

Adjusting energy intake during periods of high training or competition

When training intensity or volume increases—such as during heavy training blocks or competition—the body burns more energy and requires additional protein, carbohydrate, and fat to support performance and recovery.

During these periods, it’s recommended to:

• Increase total caloric intake by 10–50%, depending on training intensity
• Keep fat at the same percentage of total calories
• Increase protein to 2 g/kg/day (or 0.91 g/lb/day) to support recovery
• Fill in the remainder with carbohydrates to replenish glycogen and fuel training

These tweaks to your plan will ensure you are optimising your recovery during these periods of heavier training demand.

Why Protein Recommendations Are Based on Body Mass, Not a Percentage of Energy Intake

Protein requirements are based on body mass because protein’s primary role is to support muscle repair and maintenance—not to provide energy. In contrast, fats support both energy needs and essential bodily functions, while carbohydrates are the body’s main energy source, especially during endurance training.

If you base protein intake on a percentage of total energy (e.g., 20%), it can lead to values that are either excessively high or too low. For example, someone burning 5000 kcal per day would consume 250g of protein at 20%—an unnecessarily large and potentially wasteful amount. Conversely, someone consuming just 1800 kcal per day would only get 90g of protein at 20%, which may be insufficient for anyone over 120 lbs. This is why the scientific literature used to design this calculator expresses protein needs as a fixed amount per unit of body mass. Protein requirements are more closely related to body weight, particularly lean mass, than to energy expenditure, because body mass influences the amount of muscle that needs to be maintained and repaired. Carbohydrate and fat needs, however, must scale with energy expenditure, as their utilisation is directly related to the amount of energy being burned.

This is why any recommendation such as "consume 20% protein, 30% fat, 50% carbohydrate" is invalid, reductionistic, and not an appropriate way to determine macronutrient needs for athletes.

Body composition

These macronutrient recommendations are designed for endurance-trained individuals. If you have a high body fat percentage (i.e., you are overweight), the protein requirements outlined here may be too high from a performance standpoint, as they are based on studies involving trained athletes. That said, there is no harm in consuming a higher-protein diet. However, if you are overweight, the primary focus should be on reducing total caloric intake to achieve a healthy and optimal body composition for running—after which this method can be more appropriately applied.

Individual Variation: Balancing Fat and Carbohydrate Intake

Some individuals feel and perform better with slightly higher fat intake relative to carbohydrates, and this often comes down to personal preference, and how one responds to different macronutrient profiles. That said, it’s important to avoid extremes on either end of the spectrum. Avoid going very high in fat (i.e., above 35% of total daily energy intake), as this can reduce carbohydrate availability needed for endurance performance. Likewise, very high-carbohydrate diets with very low fat (i.e., below 15%) may compromise hormone function, fat-soluble vitamin absorption, and overall health. There’s some flexibility here based on personal preference and training type. For example, longer, lower-intensity training sessions may allow for a slightly higher fat intake (up to ~30%), whereas high-intensity or interval-based training typically benefits from greater carbohydrate availability. However, it’s important to note that increasing fat intake at the expense of carbohydrates, in an effort to become "fat-adapted", has been shown in numerous studies to impair endurance performance (1, 2, 3, 4, 5, 6). Carbohydrates are the body’s most efficient and readily available fuel source during high-intensity efforts. For this reason, adopting a high-fat, low-carbohydrate diet is not recommended for endurance athletes aiming to optimise performance.

Individual variation (high and low daily energy expenditure)

Another important point to note is that if you have a very high daily energy expenditure due to high training volume and/or a high metabolic rate—or a very low energy expenditure from a low metabolic rate, your percentage macronutrient values may fall outside the typical recommended ranges.

Low energy expenditure (daily needs <2000 kcals)

For those with a very low daily energy requirement, say, 1800 kcals, they may require a fat intake above 20% for optimal health. For example, 20% of 1800 kcals is just 360 kcals, or 40 grams of fat. If this person weighs 200 lbs, that equates to only 0.2 g/lb of fat, which is widely considered too low to support essential functions like hormone production, fat-soluble vitamin absorption (A, D, E, and K), and immune health. 

High energy expenditure (daily needs >3000 kcals)

Athletes who train intensely for long durations have been shown to consume well over 4000 kcals per day to sustain their energy needs and body mass (McArdle et al.). Because the protein recommendation of 0.82 g/lb of body mass is a fixed value based on weight, protein will account for a lower percentage of total energy intake in athletes with higher caloric needs. In other words, as total energy intake increases, protein remains relatively stable in absolute terms (grams), but decreases as a percentage of total kcals. This is because protein is calculated based on body mass, not as a percentage of energy. If you’re training hard and burning a large amount of energy each day, your calculated macronutrient split will result in a higher percentage of carbohydrates—often exceeding 60% of daily intake. This is essential for supporting training demands and replenishing glycogen stores (McArdle et al., 2015).

Meeting your macronutrient targets, especially protein, is much easier when you have a higher daily energy expenditure, as you're able to consume more total food. I fall into this category myself, with a daily intake of around 3200 kcals. If your energy needs are lower, it becomes more difficult to hit optimal macronutrient levels, as there's less room for error and the diet must be less calorie-dense and more nutrient-focused. With this in mind, if you have a lower daily energy expenditure, it may be beneficial to increase it. This can be achieved by building lean muscle mass, increasing training volume, or boosting non-exercise activity, such as walking more throughout the day.

Supplementation

Consuming optimal protein levels through diet alone can be challenging, which is why protein powders exist. At Thrive, we offer both plant-based protein and whey protein isolate, both scientifically designed to provide all the essential amino acids needed for recovery. Our proteins are made with the cleanest ingredients, taste amazing, are third-party tested, and proudly made in Canada.

About the Author:

Joe is a certified personal trainer, strength and conditioning coach, and nutrition coach. He holds a Bachelor of Science with Honours in Sport and Exercise Science, graduating with First Class standing. During his studies, Joe focused on human physiology and performance, and he applies this knowledge of exercise science to his work with Thrive. He is the co-founder of Thrive Protein, a Canadian family-run supplement company focused on clean, scientifically backed nutrition products — including protein powders, greens, and electrolytes.

References

PROTEIN

Houltham, S. D., & Rowlands, D. S. (2014). A snapshot of nitrogen balance in endurance-trained women. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme,39(2), 219–225. Link

Kato, H., Suzuki, K., Bannai, M., & Moore, D. R. (2016). Protein Requirements Are Elevated in Endurance Athletes after Exercise as Determined by the Indicator Amino Acid Oxidation Method.PloS one,11(6), e0157406. Link

Williamson, E., Fung, H. J. W., Adams, C., West, D. W. D., & Moore, D. R. (2023). Protein Requirements Are Increased in Endurance-Trained Athletes but Similar between Females and Males during Postexercise Recovery.Medicine and science in sports and exercise,55(10), 1866–1875. Link

CARBOHYDRATE AND FAT

McArdle, W. D., Katch, F. I., & Katch, V. L. (2015). Exercise physiology : nutrition, energy, and human performance(8th ed). Wolters Kluwer Health/Lippincott Williams & Wilkins.

Jeukendrup, Asker. (2003). High-carbohydrate versus high-fat diets in endurance sports. Schweizerische Zeitschrift fur Sportmedizin und Sporttraumatologie. 51. Link

Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance.Journal of the Academy of Nutrition and Dietetics,116(3), 501–528. Link

LOW CARBOHYDRATE TRAINING