Weight Gain Calculator
Calculate your daily calorie needs for healthy weight gain using Mifflin-St Jeor BMR formula. Get TDEE, calorie surplus, weekly weight progression, and time to reach your goal weight.
About This Calculator
The Weight Gain Calculator helps you estimate how many calories you need to eat each day to reach your target weight at a healthy pace. Whether you are underweight, an athlete looking to build muscle, or recovering from illness, this calculator provides personalized nutrition targets based on your age, gender, height, current weight, and activity level.
The calculator uses the Mifflin-St Jeor formula, considered the most accurate equation for estimating Basal Metabolic Rate (BMR). For males: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For females: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. Your BMR is then multiplied by your activity factor (1.2 for sedentary to 1.9 for very active) to calculate your Total Daily Energy Expenditure (TDEE), which represents your maintenance calories. A calorie surplus is added based on your chosen weight gain pace — approximately 550 kcal/day for 0.5 kg per week or 1100 kcal/day for 1 kg per week (since 1 kg of body weight is roughly equivalent to 7700 kcal).
Regional Notes
India: Being underweight affects approximately 15-20% of Indian adults, particularly in rural areas. Common causes include inadequate calorie intake, chronic infections, and gastrointestinal conditions. A balanced Indian diet rich in dal, rice, roti, ghee, nuts, and milk can support healthy weight gain. Consulting a dietitian is recommended as many traditional Indian vegetarian diets may be lower in protein and calorie density.
US: About 2% of US adults are underweight. Weight gain is often pursued for muscle building, athletic performance, or recovery from illness. The Dietary Guidelines for Americans recommend a balanced approach with emphasis on lean proteins, whole grains, and healthy fats. Strength training combined with a calorie surplus is the standard recommendation for healthy weight gain.
UK: The NHS defines underweight as a BMI below 18.5, affecting about 3-4% of UK adults. The NHS Eatwell Guide provides recommendations for a balanced diet, including starchy carbohydrates, proteins, dairy, and healthy fats. Those with a BMI under 18.5 are advised to consult their GP before starting a weight gain program.
Frequently Asked Questions
How many calories do I need to eat to gain weight?
To gain weight, you need to eat more calories than your Total Daily Energy Expenditure (TDEE). A surplus of approximately 500-1100 calories per day above your maintenance level results in gaining 0.5-1 kg per week. Your exact needs depend on your age, gender, weight, height, and activity level, which the calculator uses to determine your personalized intake.
How does the weight gain calculator work?
The calculator uses the Mifflin-St Jeor formula to estimate your Basal Metabolic Rate (BMR), then multiplies it by your activity level to find your Total Daily Energy Expenditure (TDEE). It then adds a calorie surplus based on your chosen weight gain pace (0.5 kg or 1 kg per week) to determine your daily calorie intake target for healthy weight gain.
Is it safe to gain 1 kg per week?
Gaining 1 kg (2 lbs) per week is generally safe for most people who are underweight, as long as the calorie surplus comes from nutritious foods. However, a slower pace of 0.5 kg (1 lb) per week is often recommended for more sustainable weight gain. It is important to consult a healthcare provider or dietitian before starting any weight gain program, especially if you have a history of malnutrition or eating disorders.
What is the Mifflin-St Jeor formula for BMR?
For males: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. For females: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. This is considered the most accurate formula for estimating basal metabolic rate in the general population.
What should I eat to gain weight healthily?
Focus on nutrient-dense, energy-rich foods: lean proteins like chicken, fish, eggs, and legumes; healthy fats from nuts, seeds, avocados, and olive oil; complex carbohydrates like whole grains, brown rice, oats, and sweet potatoes; and calorie-dense snacks like nut butters, dried fruit, and smoothies. Avoid empty calories from processed foods and sugary drinks.
What are the risks of being underweight?
Being underweight (BMI below 18.5) can carry health risks including malnutrition, vitamin deficiencies, weakened immune function, osteoporosis, decreased fertility, and increased risk of complications from surgery. In India, US, and UK, about 2-5% of adults are underweight. Gaining weight through a balanced diet and strength training can help reduce these risks.
Do I need to exercise while trying to gain weight?
Yes, strength training is recommended during weight gain to ensure most of the weight gained is muscle rather than fat. Compound exercises like squats, deadlifts, bench press, and rows stimulate muscle growth. Aim for 3-4 strength sessions per week. Since exercise burns calories, you will need to increase your calorie intake further to compensate for the energy expended during workouts.
How long will it take me to reach my goal weight?
The time depends on the amount of weight you need to gain and your chosen pace. For example, gaining 5 kg at a normal pace of 0.5 kg per week takes approximately 10 weeks. At a strict pace of 1 kg per week, it takes about 5 weeks. The calculator shows your personalized weekly progression from start to goal.