Calorie Calculator – Estimates for Weight Loss or Weight Gain

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Calorie Calculator – Estimates for Weight Loss or Weight Gain

Photo - Woman loses weight. The calorie calculator estimates a calorie deficit for weight loss.
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Our calorie calculator helps you understand how many calories you burn each day and estimates how many calories you should consume to achieve your weight loss or weight gain goal. It outputs up to 4 levels of weight loss or gain and provides an estimated number of weeks it will take to hit your target weight.

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The calculation is based on your age, gender, height, weight and your level of physical activity. This produces a fairly accurate estimate for most people looking to lose weight, gain weight or maintain their current weight.

How does the calorie calculator work?

The calorie calculator works by taking a number of inputs about you. This includes your height and your current and target weight, as well as your gender, age and activity level.

1. BMR

This first step of the calculation is estimating your Basal Metabolic Rate (BMR). This is the number of calories your body burns at rest. This does not include the calories you burn through physical activity nor the impact of digesting food after you have eaten.

2. TDEE

Once we have an estimate of your BMR, we then calculate your Total Daily Energy Expenditure (TDEE) estimate. TDEE is a measure of how many calories you burn per day, adding together your BMR along with the calories you burn through physical activity. Because TDEE takes into account your activity level (i.e. whether you are sedentary, lightly active, moderately active, etc), it’s a more accurate estimate of your daily calorie burn.

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3. Weight loss or gain

If you don’t enter a weight loss or weight gain target, the calculator will assume you wish to maintain weight. It will output your TDEE estimate.

If you have a weight loss or weight gain goal, the calculator will provide additional information. The calculator will show results for 0.25 kg (0.6 lb), 0.5 kg (1.1 lb), 0.75 kg (1.7 lb) and 1 kg (2.2 lb) increments of weight loss or gain per week. For each of these increments, it will display the number of calories needed to reach your goal. It will also estimate the number of weeks it will take to reach your goal.

The calculator will not display any estimates below 1,200 calories for women and 1,500 calories for men. Eating at or below these number of calories is unsafe and you should always consult a doctor or suitably-qualified medical professional before engaging in extreme weight loss plans.

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How is BMR calculated?

BMR, or Basal Metabolic Rate, is the number of calories your body needs at total rest to power your most basic functions. This includes the baseline activity of your organs, but does not include the digestion of food. It also doesn’t include any calories you need for physical activity and exercise.

BMR typically increases with your weight and height, because you have a larger body mass to support. However, you can expect your BMR to decrease over time as you age. This is because most people lose muscle mass and gain fat as they age.

A number of formulas for estimating BMR have been created over time. These formulas are produced by statistical studies that look at representative populations, measuring their BMR and crunching the data to build accurate formulas.

Our calculator uses the Mifflin-St Jeor equation, which came out of a 1990 study of 498 people across both genders, all age groups and normal weight and obese persons. The study introduced a formula based on a person’s weight, height, age and gender.

For men, the formula is 9.99 x Weight + 6.25 x Height – 4.92 x Age + 5.

For women, the formula is 9.99 x Weight + 6.25 x Height – 4.92 x Age – 161.

Is Mifflin-St Jeor accurate?

BMR calculators using Mifflin-St Jeor are fairly accurate for most people. The formula, however, does not account for specific factors like muscle mass. Specifically, if you have a high muscle mass, you may find that Mifflin-St Jeor underestimates your BMR. This is because muscle burns more calories than fat cells at rest.

If you are overweight or obese, it’s likely that Mifflin-St Jeor will overestimate your BMR.

A study published in the Journal of the American Dietetic Association concluded that the Mifflin-St Jeor equation was more likely to estimate calorie needs to within 10% compared to other equations.

How is TDEE calculated?

Our calorie calculator estimates your TDEE by multiplying your BMR by an activity level. The activity levels are called Harris-Benedict Standard Activity Factor (SAF) scores, and they range from 1.2 (+20%) to 1.9 (+90%), depending on your level of physical activity.

To estimate your TDEE, you will need to determine which SAF score fits your lifestyle best:

  • Sedentary (SAF = 1.2) – Your daily life involves little to no exercise. You may work a desk-based job and spend your spare time indoors with little physical activity.
  • Light Activity (SAF = 1.375) – You take part in light exercise or sports 1-3 days per week. If you work in a job where you spend time on your feet for most of the day, this may be an appropriate factor.
  • Moderate Activity (SAF = 1.55) – You take part in moderate exercise or sports 3-5 days per week. This can include activities like jogging, cycling or swimming for at least 30 minutes each day.
  • Very Active (SAF = 1.725) – You take part in moderate-to-vigorous exercise or sports 6-7 days per week. This can include running or playing competitive sports.
  • Extra Active (SAF = 1.9) – You take part in vigorous training two times a day or have job requiring hard physical labor.
Standard Activity Factors - SAFs adjust the calorie estimate by multiplying your BMR

How is TDEE adjusted for weight loss and gain?

There are a number of ways to adjust TDEE to reflect a weight loss or weight gain goal. A popular rule-of-thumb relies on the fact that 0.45 kg (1 lb) of fat is equivalent to 3,500 calories. Many people therefore beleive that maintaining a calorie deficit of 500 calories per day (3,500 divided by 7) will allow you to lose 0.45 kg per week. You can use this idea to adjust the deficit or excess up and down to evaluate the impact it will have on your weight loss or weight gain goal.

In reality, weight loss is not that simple and it is impossible to estimate an accurate deficit or excess for most people. This rule has some disadvantages and may not be accurate for long-term weight loss plans. However, it is a reasonable starting point for many people.

Our calculator uses this principle to produce its estimates. Once you have started your weight plan, you should review your progress after 3-4 weeks and adjust your calorie intake accordingly.

Macro breakdown

When planning your diet, your macros are essential. Your macro breakdown is the proportion of your diet made up of carbohydrates, proteins and fats. Carbs provide your body with easy-to-use energy, proteins are the essential building blocks for your muscles and other body tissue and fats help support cell growth, nutrient absorption and the production of hormones.

Our macro calculator is a simple way to get macro estimates (in grams per day) of each macro. It takes into account your current body weight, and sets a minimum protein intake based on nutritional recommendations. It then adjusts your fat and carbohydrate macros to make your overall intake as balanced as possible given your calorie deficit or excess.

Tips for safe weight loss

Minimum calorie intake

If you are pregnant, have an eating disorder or have any pre-existing medical condition, you should consult a doctor or suitably-qualified medical professional for advice.

In all cases, extreme methods of weight loss can be dangerous and have serious health consequences. You should never consume less than 1,200 calories per day if you are a woman and never less than 1,500 calories if you are a man.

Is it safe to lose more than 1 kg (2 lb) per week?

Most people looking to lose weight should try to lose around 0.25 kg to 0.5 kg per week. Losing weight quickly is dangerous and can have serious health consequences. In general, most people should not attempt to lose more than 1 kg (2 lb) per week without medical supervision.

Can I lose weight without cutting calories?

Yes! Remember, the key to weight loss is maintaining a calorie deficit relative to your total daily energy expenditure (TDEE). That means you have two tools for weight loss – reducing your calorie intake or increasing your TDEE. You can increase your TDEE by increasing your activity level. Engaging in regular physical exercise will increase your TDEE.

Who should not use the calorie calculator?

Do not use our calorie calculator:

  • If you are pregnant – Our calorie calculator will not provide an accurate reflection of your health status as your body undergoes significant changes during pregnancy. Consult a doctor or medical professional if you are concerned about your weight.
  • If you have an eating disorder – Always consult a medical professional about your weight.
  • If you are under the age of 18 – BMR and TDEE estimates are not a suitable measure for children and teens under the age of 18.

References

Keys, A., Taylor, H. L., & Grande, F. (1973). Basal metabolism and age of adult man. Metabolism, 22(4), 579-587.

Fabio Comana, M. S., & PES, C. Comparing Energy Expenditure Prediction Equations.

Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American journal of clinical nutrition, 51(2), 241-247.

Frankenfield, D., Roth-Yousey, L., Compher, C., & Evidence Analysis Working Group. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic association, 105(5), 775-789.

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