Weight Gain Calculator
Calculate your daily calorie needs and get a personalized plan for healthy weight gain based on your body stats and activity level.
Enter your current weight, target weight, height, age, gender, and activity level to get your daily calorie target, calorie surplus, and optimal macronutrient breakdown.
Weight Gain Calculator
Calculate your daily calorie needs and get a personalized plan for healthy weight gain based on your body stats and activity level.
About the Weight Gain Calculator
The Weight Gain Calculator is a science-backed tool designed to help individuals who need to increase their body weight in a healthy and controlled manner. Whether you are underweight, recovering from illness, looking to build muscle, or simply trying to reach a healthier body composition, this calculator takes the guesswork out of nutrition planning by translating your personal measurements into a concrete daily calorie target.
The calculation starts with the Mifflin-St Jeor equation, one of the most widely validated formulas for estimating Basal Metabolic Rate (BMR). BMR represents the number of calories your body needs at complete rest to maintain basic physiological functions such as breathing, circulation, and cell repair. For men, the formula is: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. For women it is: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161.
Once the BMR is established, an activity multiplier is applied to estimate Total Daily Energy Expenditure (TDEE). TDEE represents the total calories you actually burn in a day, accounting for your lifestyle and exercise habits. A sedentary person who exercises rarely has a TDEE of about 1.2 × BMR, while someone who works a physically demanding job and exercises intensely can have a TDEE of 1.9 × BMR or more.
To gain weight, you need to consume more calories than your TDEE — this is called a calorie surplus. The size of the surplus determines how fast you gain weight. Each kilogram of body mass requires approximately 7,700 kcal of surplus energy, so a daily surplus of roughly 550 kcal will produce about 0.5 kg of weight gain per week. This calculator lets you choose your desired weekly rate and automatically computes the corresponding daily calorie target.
Along with your calorie target, the calculator provides a macronutrient breakdown. Protein is set at approximately 2 g per kilogram of current body weight, which is the range recommended for muscle preservation and growth during a calorie surplus. Fats contribute roughly 30% of total calories (9 kcal per gram), and the remaining calories come from carbohydrates (4 kcal per gram). This balanced distribution supports energy, hormone production, and lean mass development.
A healthy rate of weight gain is typically 0.25–0.75 kg per week. Faster rates can lead to excessive fat accumulation, insulin resistance, and joint stress, while slower rates are more likely to consist of lean tissue. The estimated time to reach your target weight assumes a constant gain rate, but real-world progress will vary due to metabolic adaptation, hydration, and body composition changes. Use this tool as a starting point, monitor your progress weekly, and adjust your intake as needed in consultation with a healthcare professional.
Weight Gain Plan Examples
Click any example button below to load realistic scenarios into the calculator.
| Profile | Daily Target | Notes |
|---|---|---|
| Male, 60 kg → 70 kg, 175 cm, 25 y, moderate activity, 0.5 kg/week | ~2,989 kcal/day (+550 surplus) | A balanced approach achieving 10 kg gain in about 20 weeks with moderate fat accumulation. |
| Female, 55 kg → 62 kg, 165 cm, 22 y, light activity, 0.25 kg/week | ~2,076 kcal/day (+275 surplus) | Conservative gain minimizing fat accumulation; reaches target in about 28 weeks. |
| Male, 70 kg → 80 kg, 180 cm, 28 y, very active, 0.75 kg/week | ~4,036 kcal/day (+825 surplus) | Aggressive muscle-building protocol for an active individual; 10 kg in roughly 13 weeks. |
| Female, 50 kg → 58 kg, 160 cm, 35 y, sedentary, 0.5 kg/week | ~1,947 kcal/day (+550 surplus) | Recovery-focused plan; sedentary activity reflects limited mobility during rehabilitation. |
How to use the Weight Gain Calculator
- Enter your current weight in kilograms and your target weight. Target weight must be higher than current weight.
- Enter your height in centimeters and your age in years. These are used to calculate your basal metabolic rate with the Mifflin-St Jeor formula.
- Select your biological gender and your typical daily activity level from the dropdown menus.
- Choose your desired weekly weight gain rate. 0.5 kg/week is a good starting point for most people.
- Click Calculate Weight Gain Plan to see your daily calorie target, calorie surplus, estimated weeks to goal, and macronutrient breakdown.
Frequently asked questions
How many extra calories do I need to gain 1 kg?
One kilogram of body weight is equivalent to approximately 7,700 kcal. To gain 1 kg per week, you need a daily surplus of about 1,100 kcal, which is a lot and will likely include significant fat gain. A more manageable target is 0.5 kg/week, requiring only about 550 extra kcal per day. Spreading the surplus across meals and emphasizing protein-rich foods helps ensure most of the gain is lean mass.
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation estimates your Basal Metabolic Rate (BMR) — the calories your body burns at rest. It uses weight, height, age, and sex as inputs and is considered more accurate than the older Harris-Benedict formula. After calculating BMR, an activity multiplier is applied to get your Total Daily Energy Expenditure (TDEE), which forms the base for the weight gain calorie target.
How fast should I aim to gain weight?
Most health and nutrition experts recommend gaining 0.25–0.75 kg per week for healthy weight gain. Rates above 1 kg per week tend to accumulate excess body fat and can strain the cardiovascular system and joints. Slower rates, especially 0.25–0.5 kg per week, result in a better ratio of lean mass to fat gain and are easier to sustain over time.
Why does my activity level matter so much?
Activity level significantly affects how many calories you burn each day. A sedentary person and a very active person of the same size can have a TDEE difference of 800–1,000 kcal or more. If you underestimate your activity level, your calorie target will be too low and you may not gain weight as expected. Conversely, overestimating leads to eating more than necessary, which increases fat gain.
How much protein do I need when trying to gain weight?
For muscle growth and lean mass gain, research supports protein intakes of 1.6–2.2 g per kilogram of body weight per day. This calculator uses 2 g/kg as a practical target. Protein is essential not just for muscle synthesis but also for satiety and metabolic support. Distributing protein across 3–5 meals per day maximizes muscle protein synthesis throughout the day.
Is this calculator a substitute for medical advice?
No. The calculator provides an estimate based on established equations and standard assumptions. Individual metabolic rates, medical conditions (such as hyperthyroidism, Crohn's disease, or cancer), medication use, and body composition all affect actual calorie needs. Always consult a registered dietitian or physician before starting any significant dietary change, especially if you have an underlying health condition.