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ISSA, International Sports Sciences Association, Certified Personal Trainer, ISSAonline,  Carb Cycling Step by Step, Carb Cycling Calculator: 5 Steps to Determining Carb Intake

Carb Cycling Calculator: 5 Steps to Determining Carb Intake

Reading Time: 5 minutes 40 seconds


DATE: 2024-01-24

Carbohydrates give the body energy. You can also use carbs to help you build muscle. Yet, many people have negative thoughts about this macronutrient. Some associate eating carbs with weight gain. Others feel that they can’t be part of a healthy diet—not ever.

Neither of these statements is true. You can still enjoy carbohydrate-containing foods without worrying that they will hurt your body weight or body composition. One way to do this is by engaging in a practice called carb cycling.

What Carb Cycling Is

Carb cycling involves changing your carb intake from day to day. You cycle back and forth, eating high carb on certain days and low carb on others. Then there are the days that you might have a moderate carb intake.

Your carb intake for a specific day depends on your activity level. If you plan to do a long or intense workout, a high carb day can supply the energy your body needs. If your activity is light, you might want a medium carb day. If you’re taking a rest day, this would be a good low carb day.

Benefits of Following a Carb Cycling Diet

Some people feel that the best way to lose weight is to follow a low carb diet. The problem with this approach is that your body will adapt.

This adaptation slows chemical reactions in the body. It also downregulates your thyroid, which is responsible for fat loss. It even downregulates leptin, the hormone that tells your brain when you’ve eaten enough. In short, over time, simply cutting your carb intake will stall weight loss. You’ll hit a plateau, which can be frustrating.

Carb cycling keeps your body from adapting. Your body can’t adjust because one day you might eat high carb, then eating low carb the next. This offsets the natural adaptation process. The result is higher leptin levels and increased metabolism.

One study involving 24 physically active people involved participants alternating between a low carb and high carb diet. Subjects had a significant reduction in body mass. They also experienced fat loss and better performance.

Carb Cycling Calculator

If you or your client would like to try carb cycling, you need to calculate how many carbs you will consume on both low carb and high carb days. This 5-step carb cycling calculator can help:

Step #1: Calculate Your Basal Metabolic Rate

Basal metabolic rate (BMR) is how much energy your body uses simply to survive. The calculation for BMR varies based on sex:

  • Men: BMR = 66 + (13.7 x weight in kg) + (5 x height in cm) – (6.8 x age)

  • Women: BMR = 655 + (9.6 x weight in kg) + (1.7 x height in cm) – (4.7 x age)

Step #2: Add In Your Physical Activity Level

Now that you know your BMR, the next step is to consider your level of physical activity. This tells you how much energy your body uses based on how active you typically are. 

To add in your physical activity level, you multiply your BMR by the corresponding activity level factor. This factor is determined by the exercise type and intensity.

Image of a table

Step #3: Determine Your Protein and Fat Breakdown

During this step, you will determine your protein and fat intake. You start by determining how many grams of each you need. Then, you convert the grams into a calorie number. These formulas can help:

  • Protein: (Body weight x 1.15 grams of protein) x 4 calories per gram = daily protein calorie goal

  • Fat: (Body weight x 0.30 grams of fat) x 9 calories per gram – daily fat calorie goal

Add these numbers together, then subtract them from your total calorie intake. This will tell you how many carb calories you should consume daily. Divide this number by four to turn this calorie count into grams.

Step #4: Calculate Your Carb Cycling Amounts

Now you are ready to calculate what each carb cycle day will look like in terms of intake. 

  • High carb day: Keep your intake at the number just calculated. Essentially, your recommended carb intake is the amount you want to aim for on a high carb day.

  • Medium carb day: Lower your intake by 15-20%. To find this amount, multiply your recommended carb intake by 0.8 and 0.85. Your intake on a medium carb day should be somewhere between these two amounts.

  • Low carb day: Decrease your medium carb intake by 20-25%. To find this amount, multiply the medium carb intake by 0.75 and 0.8. Your intake on a low carb day should be between these amounts.

Step #5: Adjust Intake as Needed

Every three or four weeks, evaluate how your carb cycling is working. Are you still progressing toward your weight loss goals? If not, you might have to make modifications to get better results.

In addition to paying attention to weight, consider other progress as well. This can include body measurements, clothes fitting looser, and having more energy. Fat loss doesn’t always show up on the scale.

Quick Recap: To use a carb cycling approach, you need to figure out your total caloric intake. Then you break down your daily calorie intake to determine how much protein and fat you need. Next, you determine your carb cycling amounts. As your diet progresses, you can modify these amounts.

About Using Apps to Help Determine Carb Intake

If you want to take advantage of carb cycling but don’t want to calculate them on your own, some apps can help you determine your intake amounts. 

New apps are being created all the time. Before trying one, read its reviews. What do actual users have to say about it? How does the app work? Does it even work? Is it more frustrating than useful? Do you have to pay for the app or is it free?

Answering these types of questions can help you pick the best carb cycling app for you.

Do I Have to Calculate My Carbohydrate Intake to Get Results?

For some, the idea of using a carb cycling calculator is enough to forget counting carbohydrates altogether. Plus, not everyone has a desire to follow a strict carb schedule. If either applies to you or your client, another option is simply to incorporate cheat meals or “refeed days.”

While not as precise, a cheat meal or refeed day can help prevent adaptation by changing your normal carb intake. To do this without hindering your weight loss, eat low carb for several days before. Then, on the cheat or feed day, eat high carb—or between five and 10 times higher than your typical intake.

It can also be helpful to increase your protein and fat intake on these days as well. Protein assists with muscle gain and recovery. Healthy fats reduce your risk of disease. They also aid in the absorption of fat-soluble vitamins.

Exercising When You Are Carbohydrate Cycling

Remember that your carb intake is dependent on your activity level. Therefore, it’s important that you plan your carb cycling around your exercise program.

Make note of the days when your workouts are intense. Maybe you plan to do a long workout to build your endurance. Or you will increase the weight you lift to boost your muscle mass. Plan to eat high carb on these days.

If you’re doing moderate intensity activity on a certain day, this is a good day for medium carb intake. Likewise, a low activity day is perfect for eating low carb.

One Final Word About Carb Cycling

Carb cycling isn’t going to lead to fat loss on its own. Several other factors come into play. Having a calorie deficit is important. Plus, the greater your lean mass, the more energy your body needs. So, building muscle will aid in fat loss too.

If you’re not getting the results you want, you may need to consider what is going on. Are you being realistic about how active you are? Are you overeating in other areas, such as exceeding your desired protein intake? 

Earning your Nutrition certification can help you provide clients with more personalized diet advice. This course does a deep dive into different carb types (i.e., simple carbohydrates versus complex carbs). It also teaches you how to create a healthy meal plan that will meet a client’s nutritional needs while helping them reduce body fat.

Featured Course

ISSA | Nutritionist

By becoming an ISSA Nutritionist, you'll learn the foundations of how food fuels the body, plus step by step methods for implementing a healthy eating plan into clients' lifestyles.


Wachsmuth, N., Aberer, F., Haupt, S., Schierbauer, J., Zimmer, R., & Eckstein, M. et al. (2022). The Impact of a High-Carbohydrate/Low Fat vs. Low-Carbohydrate Diet on Performance and Body Composition in Physically Active Adults: A Cross-Over Controlled Trial. Nutrients, 14(3), 423. https://doi.org/10.3390/nu14030423

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