How many calories should I eat to gain weight?

Most people need a surplus of 250–500 kcal per day above their maintenance calories to gain 0.25–0.5 kg (0.5–1 lb) per week. This calculator estimates your maintenance using your age, sex, height, weight, and activity level, then adds the surplus needed for your chosen rate of weight gain.

How fast can I safely gain weight?

A common safe range for adults is 0.25–0.5 kg (0.5–1 lb) per week. Faster gain usually means a higher proportion of fat and water instead of lean mass. Underweight people or those recovering from illness may be advised differently by a clinician.

How much protein do I need to build muscle?

For most healthy adults doing resistance training, 1.6–2.2 g of protein per kg of body weight per day is commonly recommended in sports nutrition research. This calculator uses a default of 1.8 g/kg, which you can adjust if needed.

Will this calculator work if I am underweight?

Yes, it can give you a structured calorie and macro target. However, if you are significantly underweight, have a medical condition, or a history of disordered eating, you should use this only as a rough guide and work with a healthcare professional or registered dietitian.

Do I need to exercise to gain weight?

You can gain weight without exercise by eating in a calorie surplus, but much of the gain may be fat. Combining a moderate calorie surplus with resistance training (e.g., weight lifting) helps more of the gain be lean mass (muscle and bone).

Weight Gain Calculator

Find out exactly how many calories and macros you need each day to gain weight or build muscle at your chosen pace.

Units

Metric (kg, cm) Imperial (lb, ft/in)

Sex

Male Female

Age

years

Height

Current weight

Goal weight

Goal must be higher than current weight.

Timeframe

weeks

We’ll calculate the weekly gain and daily surplus.

Activity level

Macro targets

Defaults are based on common sports nutrition guidelines for lean weight gain.

Protein

g/kg

Fat

% of calories

Carbs

Calculated as the remaining calories after protein and fat.

Your weight gain plan

Weekly gain

–

Maintenance calories

– kcal/day

Estimated to keep your current weight stable.

Target calories

– kcal/day

–

Daily macro breakdown

Protein

– g/day

– kcal (–%)

Fat

– g/day

– kcal (–%)

Carbohydrates

– g/day

– kcal (–%)

Projected weight over time

Assuming you consistently hit your calorie target.

Week	Projected weight	Change from start

How this weight gain calculator works

This tool estimates how many calories you need to maintain your current weight, then adds the extra energy required to reach your goal weight in your chosen timeframe. It also converts those calories into daily protein, fat, and carbohydrate targets.

1. Step 1 – Estimate your maintenance calories (TDEE)

First we estimate your Basal Metabolic Rate (BMR) using the Mifflin–St Jeor equation, which is widely used in nutrition research:

For men: \( \text{BMR} = 10 \times \text{weight}_{kg} + 6.25 \times \text{height}_{cm} - 5 \times \text{age} + 5 \)

For women: \( \text{BMR} = 10 \times \text{weight}_{kg} + 6.25 \times \text{height}_{cm} - 5 \times \text{age} - 161 \)

Then we multiply BMR by an activity factor to get your Total Daily Energy Expenditure (TDEE):

Sedentary: 1.2
Lightly active: 1.375
Moderately active: 1.55
Very active: 1.725
Extra active: 1.9

\( \text{TDEE} = \text{BMR} \times \text{activity factor} \)

2. Step 2 – Calculate the required calorie surplus

The calculator compares your current weight and goal weight to find the total weight you want to gain:

\( \Delta W = W_{\text{goal}} - W_{\text{current}} \)

\( \text{Weekly gain} = \Delta W / \text{weeks} \)

We then convert your weekly gain into a daily calorie surplus. A common approximation is that gaining 1 kg of body weight requires about 7,700 kcal:

\( \text{Daily surplus} \approx \frac{\text{Weekly gain}_{kg} \times 7700}{7} \)

\( \text{Target calories} = \text{TDEE} + \text{Daily surplus} \)

If your requested rate of gain is very aggressive, the calculator will warn you that the plan may be unrealistic or unhealthy.

3. Step 3 – Turn calories into macros

To support muscle growth and healthy weight gain, we allocate your calories into protein, fat, and carbs:

Protein: default 1.8 g per kg of body weight (you can adjust 0.8–3.0 g/kg).
Fat: default 25% of total calories (adjustable 15–40%).
Carbs: whatever calories remain after protein and fat.

\( \text{Protein kcal} = \text{Protein g} \times 4 \)

\( \text{Fat kcal} = \text{Fat g} \times 9 \)

\( \text{Carb kcal} = \text{Total kcal} - \text{Protein kcal} - \text{Fat kcal} \)

\( \text{Carb g} = \text{Carb kcal} / 4 \)

What is a healthy rate of weight gain?

For most adults, a gain of 0.25–0.5 kg (0.5–1 lb) per week is considered a reasonable and sustainable target. Faster gain usually means a larger share of fat and water instead of lean mass.

Exceptions include people who are severely underweight or recovering from illness, who may be advised to gain faster under medical supervision.

Tips for gaining weight effectively

Eat more often: 4–6 smaller meals and snacks can be easier than 2–3 huge meals.
Choose energy-dense foods: nuts, nut butters, oils, full‑fat dairy, avocado, dried fruit.
Prioritize protein: include a protein source at every meal (eggs, dairy, meat, fish, tofu, legumes).
Lift weights: resistance training helps your body turn extra calories into muscle, not just fat.
Track progress: weigh yourself 1–2 times per week under similar conditions and adjust calories if needed.

Frequently asked questions

Is it better to gain weight slowly or quickly?

Slower, steady gain is usually better for body composition and long‑term health. Rapid weight gain often leads to more fat storage and can be uncomfortable (bloating, poor appetite, reflux). A moderate surplus that you can stick to is more effective than an extreme plan you abandon after a week.

Do I have to hit my calorie target exactly every day?

No. Think in terms of weekly averages. If you are close to your target most days, your weekly average will be near the goal and your weight trend will move in the right direction.

Can I use this calculator if I have a medical condition?

This calculator is for general information and educational purposes only. It does not replace medical advice. If you have diabetes, kidney disease, digestive disorders, eating disorders, or are pregnant or breastfeeding, you should work with a healthcare professional or registered dietitian before making major changes to your diet.

What if my weight is not changing?

If your weight has been stable for 1–2 weeks while following the plan, increase your daily calories by about 150–250 kcal and monitor again. Individual energy needs can differ significantly from estimates due to genetics, NEAT (non‑exercise activity), and measurement error.

Disclaimer

This calculator provides estimates based on population formulas and should not be used as a substitute for personalized medical or nutrition advice. Always consult a qualified professional before starting any major change in diet, training, or body weight, especially if you have existing health conditions.