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Weight Gain Calculator

Accurately calculate your caloric needs to support healthy weight gain.

Weight Gain Calculator

The Weight Gain Calculator is a practical tool for anyone looking to increase body weight in a healthy and controlled manner. Whether your goal is to build muscle, improve athletic performance, or recover from underweight status, this calculator provides evidence-based guidance.

By factoring in age, sex, weight, height, activity level, and metabolism, the Weight Gain Calculator estimates the number of calories needed to gain weight safely. It helps users plan nutrition and track progress scientifically, avoiding unhealthy rapid weight gain.

Section: Understanding Weight Gain Calculator
The Weight Gain Calculator works by determining your total daily energy expenditure (TDEE) and suggesting an appropriate caloric surplus to support weight gain. This approach ensures that weight gain is primarily from lean mass rather than excess fat.

Weight Gain Calculator

Estimate how many calories you need each day to reach your target weight — based on the Mifflin–St Jeor equation and your personal activity level.

Your Profile (Step 1 of 3)
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Your Profile

Enter your biological sex, age, height and current weight. All values are used in the Mifflin–St Jeor equation to estimate your resting metabolic rate.

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Male
♀
Female
This calculator is designed for adults aged 18–120.
Please enter an age between 18 and 120.
Please enter a height between 50 and 300 cm.
Range: 15–700 kg.
Please enter a weight between 15 and 700 kg.
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Activity & Target

Select your activity level and set the weight you want to reach. Your pace determines the daily calorie surplus required each week.

Activity multipliers per the 2015–2020 U.S. Dietary Guidelines for Americans.
Must be higher than your current weight. Range: 20–300 kg.
Target must be greater than current weight (max 300 kg).
Normal pace
0.5 kg / 1 lb per week
Recommended
Faster pace
1 kg / 2 lbs per week
Aggressive

Your Daily Calorie Target

--
kcal / day
to start reaching your goal
--
Maintenance
--
Daily surplus
--
Weeks to goal

BMR

--
kcal / day at rest

TDEE

--
maintenance calories

Weight to gain

--
kg

Time to goal

--
weeks

How your calories were calculated

Formula: Mifflin–St Jeor equation (1990)
BMR (men): 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
BMR (women): 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
TDEE: BMR × activity factor (1.2 – 1.9)
Calorie surplus needed: ~7,700 kcal to gain 1 kg (3,500 kcal / lb)
Your values: --

Week-by-week plan

Week Projected weight Daily calories Cumulative surplus

Evidence-based tips to gain weight healthily

Don't skip main meals. Consistent meal timing supports anabolic signalling and prevents energy deficits.
Add energy-dense snacks. Nuts, nut butters, oat bars, avocado and seeds are calorie-rich without large volume.
Prioritise protein. Aim for 1.6–2.2 g of protein per kg of body weight per day to support lean mass gain (Morton et al., Br J Sports Med, 2018).
Time drinks carefully. Avoid large drinks immediately before or during meals if they reduce appetite.
Include resistance training. Combining a calorie surplus with strength training promotes muscle gain rather than fat accumulation (Slater & Phillips, J Sports Sci, 2011).
Recalculate regularly. Recalculate your TDEE every 4–6 weeks as your weight changes, since heavier bodies burn more calories at rest.

Activity level reference

Level Multiplier Description
Sedentary 1.20 Little or no exercise; desk job
Lightly active 1.375 Light exercise 1–3 days/week
Moderately active 1.55 Moderate exercise 3–5 days/week
Very active 1.725 Hard exercise 6–7 days/week
Extremely active 1.90 Physical job or twice-daily training
Medical disclaimer This calculator provides an estimate only. The Mifflin–St Jeor equation predicts BMR within 10% of values measured by indirect calorimetry in approximately 82% of individuals (Frankenfield et al., J Am Diet Assoc, 2005). Individual results vary due to genetics, hormones, medications and body composition. If you have a history of an eating disorder or malnutrition, consult your healthcare provider before increasing caloric intake — refeeding syndrome is a potentially life-threatening complication of rapid nutritional rehabilitation. This tool is for informational purposes only and does not constitute medical advice.

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Understanding Weight Gain Calculator

The Weight Gain Calculator works by determining your total daily energy expenditure (TDEE) and suggesting an appropriate caloric surplus to support weight gain. This approach ensures that weight gain is primarily from lean mass rather than excess fat.

Understanding caloric requirements is essential for effective weight gain. The calculator provides personalized recommendations based on basal metabolic rate, activity level, and individual goals, ensuring nutrition plans are tailored and sustainable.

In addition to calorie targets, the Weight Gain Calculator can guide macronutrient distribution, helping users balance protein, carbohydrates, and fats to optimize muscle growth and overall health. Regular tracking enables adjustments for steady progress and safe weight gain.

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    FAQ

    Understanding this calculator can raise questions. Here you’ll find clear, evidence-based answers to help you interpret your results and understand the science behind it.

    Accuracy depends on correct input data such as weight, height, age, and activity level. It provides reliable estimates suitable for planning and tracking weight gain goals.

    Yes, by combining the calculator’s recommendations with strength training and adequate protein intake, you can prioritize lean muscle gain.

    Most guidelines recommend a 250–500 kcal daily surplus for steady, healthy weight gain, minimizing excessive fat accumulation.

    Reassess every 2–4 weeks or whenever your weight changes significantly to ensure caloric recommendations remain accurate.

    The Weight Gain Calculator provides a precise, evidence-based method for planning and monitoring healthy weight gain. It empowers users to make informed decisions about nutrition, activity, and progress tracking.

    Consistent use supports steady, safe weight gain, helping individuals achieve their fitness, performance, or health goals while maintaining optimal body composition and overall wellness.

    The Weight Gain Calculator estimates the calorie surplus needed to gain weight at a healthy rate. It computes your TDEE and adds a controlled surplus to support muscle growth while minimizing fat gain.

    How to Use This Calculator

    1. Enter your age, gender, height, weight and activity level.
    2. Set your target gain rate (0.25–0.5 kg per week is optimal for lean gain).
    3. The calculator adds the required surplus to your maintenance calories.

    What the Result Means

    A surplus of 250–500 kcal/day supports 0.25–0.5 kg of weight gain per week. Combined with resistance training, most of this gain can be lean muscle rather than fat.

    Reference Values

    Lean bulk surplus: 250–350 kcal/day. Aggressive bulk: 500+ kcal/day. Protein target for muscle gain: 1.6–2.2 g/kg body weight. Realistic muscle gain: 0.5–1 kg/month for intermediates.

    Calorie Surplus vs Weight Gain Rate
    Daily SurplusWeekly GainMonthly GainType
    250 kcal~0.25 kg~1 kgLean bulk (recommended)
    350 kcal~0.35 kg~1.5 kgModerate bulk
    500 kcal~0.5 kg~2 kgAggressive bulk
    750+ kcal~0.75 kg~3 kgDirty bulk (more fat gain)