How many calories should I eat to gain weight?

Start at 300-500 above maintenance. That supports roughly 0.5-1 lb a week, which is fast enough to be visible and slow enough that a reasonable share is lean tissue.

How can I gain weight without getting fat?

Keep the surplus modest, train with weights three to five times a week, and eat 1.6-2.2 g of protein per kilogram of body weight. The size of the surplus is the main lever determining how much of the gain is fat.

Why can I not gain weight even though I eat a lot?

Almost always because intake is lower or more variable than it feels. Very lean, highly active people also burn substantially more through spontaneous movement. Track everything for a week before concluding you have a fast metabolism.

How fast should I gain weight?

About 0.25-0.5% of body weight a week for most people. Beginners and the very underweight can go faster; experienced lifters gain lean tissue too slowly for a large surplus to be useful.

Should I use weight-gain shakes?

They are a convenience, not a requirement. If chewing enough food is the bottleneck, liquid calories help because they are less filling. Whole milk, oats, nut butters and olive oil do the same job at lower cost.

Weight Gain Calculator

Work out the daily calorie surplus, protein target and timeline needed to gain weight steadily rather than sloppily.

Enter your details and your result will appear here.

What Is Weight Gain?

This weight gain calculator gives you the daily calorie intake, protein target and realistic timeline for putting on weight deliberately.

The difficulty with gaining is rarely knowing that you need to eat more. It is eating more consistently, at a rate slow enough that most of what you add is lean tissue rather than fat.

Understanding Your Weight Gain Result

A surplus works the same way a deficit does, in reverse: eat above maintenance and the extra energy is stored. What you store depends almost entirely on two things - how large the surplus is, and whether you are training.

A modest surplus of 250-350 calories a day supports roughly half a pound of gain a week. Paired with resistance training and adequate protein, a large share of that can be muscle. Push the surplus to 1,000 calories and you will gain faster, but the additional weight is disproportionately fat, and there is a ceiling on how quickly muscle can be built that no amount of extra food raises.

Beginners can realistically add 1-2 lb of muscle a month; experienced lifters closer to half that. Anything above those rates is fat, water or gut contents.

How Is Weight Gain Calculated?

Daily target = TDEE + surplus
Weekly gain (lb) = (surplus x 7) / 3500
Protein target = 1.6-2.2 g per kg of body weight

How to use this weight gain calculator

Enter your sex, age, height, current weight and activity level, then choose your target weight and pace. You will get your maintenance calories, your daily target, a protein goal and the expected timeline.

Recheck the number after four weeks. If the scale has not moved, add 200 calories and reassess - predicted maintenance is a starting point, and the scale is the actual measurement.

What affects your rate of gain

Training status is the ceiling on lean gain: beginners build muscle several times faster than experienced lifters. Protein intake determines whether the surplus has raw material to work with. Non-exercise activity often rises spontaneously when you eat more, quietly eating into the surplus.

Sleep matters more than supplements. Chronic short sleep shifts the composition of weight gained toward fat.

Eating enough when appetite is the problem

Increase the calorie density of what you already eat rather than the volume - oil, nut butter, full-fat dairy and dried fruit add hundreds of calories with little bulk. Liquid calories bypass the fullness that stops most underweight people from finishing meals.

Add one fixed extra eating occasion a day rather than trying to make every meal bigger. Consistency beats intensity here as much as anywhere else.

Methodology

BMR is calculated with Mifflin-St Jeor, multiplied by your activity factor to give maintenance, then your chosen surplus is added. Protein targets use 1.6-2.2 g per kilogram of body weight, the range consistently supported by resistance-training research.

Weekly rate uses the 3,500-calorie-per-pound approximation.

Worked Example

A 22-year-old man, 6 ft 0 in and 145 lb, moderately active, has a maintenance level around 2,600 calories. At a 400-calorie surplus he eats about 3,000 calories a day and gains roughly 0.8 lb a week.

Reaching 165 lb means 20 lb of gain, or about 25 weeks. With four resistance sessions a week and 130 g of protein a day, a meaningful proportion of that will be muscle rather than fat.

Important Limitations

Underweight people often have higher-than-predicted expenditure, so the calculated surplus may need increasing if the scale does not move after two weeks. The 3,500-calorie rule does not distinguish muscle from fat, and muscle costs more energy per pound to build. Unintentional weight loss or difficulty gaining despite a genuine surplus can signal an underlying medical issue and is worth investigating rather than out-eating.

Frequently Asked Questions

How many calories should I eat to gain weight?: Start at 300-500 above maintenance. That supports roughly 0.5-1 lb a week, which is fast enough to be visible and slow enough that a reasonable share is lean tissue.
How can I gain weight without getting fat?: Keep the surplus modest, train with weights three to five times a week, and eat 1.6-2.2 g of protein per kilogram of body weight. The size of the surplus is the main lever determining how much of the gain is fat.
Why can I not gain weight even though I eat a lot?: Almost always because intake is lower or more variable than it feels. Very lean, highly active people also burn substantially more through spontaneous movement. Track everything for a week before concluding you have a fast metabolism.
How fast should I gain weight?: About 0.25-0.5% of body weight a week for most people. Beginners and the very underweight can go faster; experienced lifters gain lean tissue too slowly for a large surplus to be useful.
Should I use weight-gain shakes?: They are a convenience, not a requirement. If chewing enough food is the bottleneck, liquid calories help because they are less filling. Whole milk, oats, nut butters and olive oil do the same job at lower cost.