Weight Gain Calculator

Estimate how many calories you need to consume and the time it will take to gain weight using the calorie surplus calculator.

How to Calculate a Calorie Surplus for Weight Gain

If you’re trying to gain weight, particularly muscle mass, then calculating the right caloric surplus is essential. A calorie surplus is when you consume more calories than your body needs for daily activities.

A caloric surplus is necessary for providing your body with the energy it needs to build muscle in order to gain weight in a healthy and sustainable way. Similar to decreasing caloric intake while trying to lose weight, you’ll need to increase your caloric intake to gain weight.

You can calculate a calorie surplus using a simple formula.

Caloric Surplus Formula

A calorie surplus is equal to calorie intake minus calories burned.

calorie surplus = calorie intake – calories burned

You should do this in a safe and calculated manner to avoid unhealthy weight gain or the development of unhealthy eating habits. You can calculate your ideal calorie surplus in a few steps.

Step One: Calculate Your Basal Metabolic Rate

Your basal metabolic rate (BMR) is the number of calories your body needs to maintain basic functions, such as breathing, heart rate, and body temperature while at rest. There are several formulas to calculate your BMR, such as the Mifflin-St Jeor and Harris-Benedict equations, which account for factors such as your age, gender, weight, and height. Research from the Journal of the American Dietetic Association notes that the Mifflin-St Jeor equation tends to be the most reliable out of the many equations available.^[1]

Mifflin-St Jeor BMR Formula

For Men:
BMR = (10 × weight [kg]) + (6.25 × height [cm]) – (5 × age [years]) + 5

For Women:
BMR = (10 × weight [kg]) + (6.25 × height [cm]) – (5 × age [years]) – 161

Step Two: Calculate Your TDEE

You also need to account for your physical activity level, which approximates the number of additional calories you burn through exercise and daily activity. You burn more or less energy the more or less active you are, and thus, require more or fewer calories based on your activity level.

This is known as your total daily energy expenditure (TDEE), and you can calculate it using a formula.

TDEE Formula

TDEE = BMR × activity factor

Thus, your TDEE is equal to your BMR times the activity factor corresponding to your general level of activity. The table below shows the activity factor corresponding to various levels of exertion:^[2]

Table showing activity factors based on physical activity level.

Level of Activity	Example	Activity Factor
Sedentary	Little to no exercise, such as a desk job with no additional physical activity	1.2
Lightly Active	Light exercise 1-2 days/week	1.375
Moderately Active	Moderate exercise 3-5 days/week	1.55
Very Active	Hard exercise 6-7 days/week	1.725
Extremely Active	Hard daily exercise and physical job or two times a day training	1.9

Step Three: Set Your Weight Gain Goal

Once you’ve found your TDEE, the next step is to set your weight gain goal. Your specific goal will depend on various factors, such as your current weight, body composition, and fitness goals.

Note: You should always consult with your doctor or a registered dietitian when setting your goal weight to ensure it’s safe and healthy.

Step Four: Calculate an Optimal Calorie Surplus

Research suggests that a safe and sustainable amount of weight gain is typically 0.25% – 0.5% of your body weight per week to minimize gains in fat mass. A hyper-energetic diet to achieve healthy weight gain should be a calorie surplus of 10% – 20%, and should contain substantial amounts of protein (1.6–2.2 g/kg/day).^[3]

How Many Calories to Gain a Pound

A general estimate is that one pound is equivalent to about 3,500 extra calories in a week for gaining fat mass; subsequently, Sanford Health notes that a goal of one pound of lean muscle requires between 2,000 and 2,500 extra calories a week.^[4] While this varies from person to person, it is a good approximation to help determine a calorie surplus for weight gain, along with your wellness goals.

Using these numbers, increasing your caloric intake by 500 calories each day could result in a weight gain of about one pound a week, depending on your goals. We need to emphasize that this is only an estimate, especially since there are several other factors that play a role in weight gain. However, it’s a good rule of thumb to use as a starting point.

Calorie Surplus Formula

Using this information, you can calculate how many additional calories you should eat to achieve your weight gain goal. Use 10% for a moderate pace to gain weight and 20% for a more aggressive pace. Note that if your goal is to add on muscle mass, then resistance training is crucial during this time period. Eating extra calories without supplemental gym time will not contribute to increased muscle mass.

Daily Calorie Surplus = TDEE × Pace

Given a reasonable daily caloric surplus, you can calculate how long it will take to achieve your weight gain goal. Multiply your surplus by the number of days in the week (7) to find your surplus per week.

Weekly Calorie Surplus = Daily Calorie Surplus × 7

Then, divide your weekly surplus by 3,500 kcal/pound to estimate the number of pounds you’ll gain per week at this pace.

Weekly Weight Gain = Weekly Calorie Surplus ÷ 3,500 (kcal/pound)

Then, divide your total weight gain goal by the weight gain per week to estimate how many weeks it will take to reach your goal.

Total Weeks = Weight Gain Goal ÷ Weekly Weight Gain

Step Five: Monitor and Adjust

It’s important to monitor your progress and adjust your caloric intake accordingly. Monitor your weight as you progress and adjust your calorie intake if your gains are outside of the 0.25% – 0.5% range of your body weight.

If you’re not gaining weight at the desired rate, you may need to increase your calorie intake slightly. Conversely, if you’re gaining weight too quickly, you may need to adjust your calorie surplus to avoid excessive fat gain.

This is also an excellent time to look at your physical activity history and routine, especially since muscle mass won’t be gained with an increase in calories and no additional resistance training.

Macronutrients

It’s crucial that you consume the right foods in your diet to ensure that your weight gain is in the form of lean mass and not fat mass. Research suggests that for lean mass weight gain, you should adjust your diet to the following macro ratios:^[5]

• 45–60% calories from carbs
• 30–35% calories from protein
• 15–30% calories from fat

You can adjust this ratio and optimize it for your goals using our macros calculator.

It’s important to keep in mind that proper bulking does not involve overeating or eating junk food. Instead, you need to focus on eating healthy, nutrient-dense foods in a calculated way. Remember to always refer back to your primary care physician or nutritionist in order to have questions answered regarding your meal plans or your overall healthcare!