How Many Calories Should You Eat to Gain Weight?

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Everyone’s caught up with weight loss – but how many calories do you need to gain weight? Especially building muscle mass?

Today we’re answering the key questions to help gain muscle mass and boost your results. We’re getting straight into the what, why, and how so you don’t waste another day gaining low-quality weight!

Short Answer: How Many Calories Should I Eat to Gain Weight?

Short Answer How Many Calories Should I Eat to Gain Weight

You should eat around 500 more calories per day to make sure you gain weight – around 110% of your maintenance calories intake. Once you find out what you need, any amount of calories consumed above that level causes weight gain.

The only real difference is how quickly you gain weight, whether that weight gain is muscle mass or fat, and how much fat you gain that you want to burn off later.

More calories produce more weight gain, and fewer produce less – but specifically less body fat.

What’s in Calories?

A calorie measures energy – the amount required to raise the temperature of 1g of water by 1-degree Celsius.

What’s in Calories

So your daily calorie intake tells you what your energy needs are and you can use that energy intake – by moving it up or down – to build muscle mass or burn body fat.

Surplus is when you consume more than you use, and deficit is when your calorie intake is below your needs. Your body either stores the excess as body fat or muscle mass, or it makes up the calorie deficit by using stored body fat as back-up fuel for exercise.

Calories Measure Energy: Using Calorie Intake for Weight Gain and Muscle Mass

Calories Measure Energy Using Calorie Intake for Weight Gain and Muscle Mass

All food has an energy value – whether it’s a healthy or unhealthy food. The calorie content is about quantity, not quality, and it’s important to remember that energy is the thing that changes body weight, while the nutrient content is what makes a food healthy or not.

Changing calorie intake only tells you how much weight gain or loss you’re going to experience, but not what that is.

Science Round-Up: Build Lean Muscle Mass

There are 4 major steps to figuring out a great weight gain diet that maximizes lean muscle mass and reduces the amount of body fat you gain:

  1. Find out how many calories you need per day to maintain weight
  2. Select a calorie surplus that helps you gain weight without increased risk of fat mass. (Here’s how to find that)
  3. Eat lots of protein, whole grains, healthy fats, and varied fruit and vegetables
  4. Maintain physical activity and lift weights regularly
  5. Sleep properly and keep your stress levels as low as possible
Science Round-Up Build Lean Muscle Mass

If you get these right, you’re likely to gain healthy weight without excess calories and unwanted fat intake. You gain lean body mass when you focus on a small calorie consumption bump, steady weight gain, and increase physical activity.

How Many Calories Should I Eat to Gain Weight?

How Many Calories Should I Eat to Gain Weight

You should eat around 500 calories per day more than your maintenance calories, according to a TDEE calculator – which uses the Harris Benedict equation to calculate basal metabolic rate and then tailors it to your physical activity levels.

For smaller people, this may only be around 2200-2500 calorie intake per day. However, much larger people could easily have a daily caloric intake of 4000+ for weight gain – especially with lots of calories burned per week through exercise.

Focus on the calories per week, and use your days to try and get around the average. You’ll have good days and bad days, but this weekly average calorie intake is the most reliable measure.

Finding Your Maintenance Calorie Intake

You need to find your maintenance ‘calories burned’ so that you can plan a weight gain diet. TDEE calculators exist to give you an estimate, based on your body fat percentage, body weight, physical activity levels, age, sex, and other factors.

Finding Your Maintenance Calorie Intake

These are a great way to get the best and most accurate starting point, but they’re not the only ways to go.

You don’t need a calorie calculator – and there are some methods that use your current weight or your weight gain goals to estimate your caloric intake.

1. Using Body Weight to Estimate Calorie Goals

Using Body Weight to Estimate Calorie Goals

You can use your current weight in pounds to get a good estimate of your calorie needs. Here’s an example:

Weight gain calorie intake = [current weight] * 15-20

This is a super rough “rule of thumb” you’ll see on some bodybuilding pages for muscle gain. It’s a simple system that you can use easily to get a number of calories to aim for.

Obviously, your body burns a different number of calories each day and this is over-simplified.

However, it’s one of the easiest ways to go. You use a higher multiple if you want to gain weight fast, and a smaller number for steady weight gain. This also changes with your body weight and activity levels.

More active people need more calories, and that means going up to the 18-20 times current weight range for lifting weights 5+ times a week, or performing high intensity intervals or sports training regularly.

2. How Much Weight Gain Do You Want?

How Much Weight Gain Do You Want

Speed of weight gain is one of the most important factors: you can gain weight fast but you’ll typically gain more body fat, and less muscle mass (relatively). On the other hand, steady weight gain is more efficient and healthy weight, but does take longer.


Figure out how much time you have and how quickly you can gain weight, and how much extra fat you’re willing to gain.

Steady weight gain doesn’t require as much fat-burning later on, so it may be the best choice if you want to build lean muscle mass and keep your body fat percentage low while you gain healthy weight.

This is all down to personal goals and how you look, feel, and perform while gaining weight matters just as much as the end result!

3. Using Goal Body Weight for Calorie Intake  

Using Goal Body Weight for Calorie Intake

Aside from your current weight, you can also use your goal body weight for weight gain estimates. A lot of high body fat percentage guys do this, as a way to aim for the protein and calorie requirements of a leaner physique.

For example, if you’re 350lbs, you don’t want to use the much-higher 15-20 multiple for caloric intake. That would feed your fat levels too much.

Equally, guys who are too skinny may not account for the added weight gain they’ll see from muscle mass during a weight gain diet.

So a 150lbs guy looking to be 200lbs may use this goal weight to estimate the number of calories per day. 3,000 calories (200*15) is a far more effective number of calories to gain weight. It’s just one more way to figure out the calories you need to build muscle mass.

4. The Calories Consumed Each Day: How Your Body Burns Fat and Energy

To maintain your current weight, your body needs to use calories from food to do a few things. The better you understand these factors, the easier it is to control weight:

  1. Your basal metabolic rate (required energy to maintain your organs)
  2. Non-exercise activity thermogenesis (all light activity that isn’t deliberate exercise)
  3. Exercise and structured physical activity
The Calories Consumed Each Day_ How Your Body Burns Fat and Energy

Each of these contributes to the calories you need and, when they change, so do the needs to maintain your current weight.

Try not to make major changes to any of these factors if weight gain is stalling. You need to think about changes here for your calorie calculator and caloric surplus: too much NEAT or exercise (without more calories) will cause weight gain to plateau.

Macronutrients: Muscle Gain vs Body Fat

Macronutrients control what weight gain is made up of – is it muscle gain or just more body fat? That depends on the speed of your weight gain, but also the things that you eat in your diet.

Macronutrients Muscle Gain vs Body Fat

Protein is the most important factor – found in lean meats and lower in processed foods – and determines muscle protein synthesis (1). This is the process that helps you build muscle mass, and ensures that muscle growth is the main cause of weight gain during a caloric surplus.

  • Protein: the stuff that makes up your muscles and responsible for muscle growth, metabolic regularity, digestive speed, and total-body repair over time.
  • Carbs: the short-term energy source that most of your calories should come from. Available in complex carbs like whole grains, or simple carbs like sugar.
  • Fats: the most calorie dense food group, so you only need a smaller amount to gain weight. Focus on healthy sources like olive oil, coconut oil, and seafood (Omega-3 fats).

Gaining weight is balanced around the type of macronutrients you eat. More protein is simple, while getting plenty of high quality carbohydrates and some healthy fats is a little harder.

You need to eat more carbs for more intense activity, while protein should just be as high as possible, and fats should be relatively constant over time.

Frequently Asked Questions

It can be hard to figure out how many calories you need to gain weight and gain lean body mass.

We’re going to answer the most common questions on the internet about muscle growth, caloric surplus, accidental weight loss, excess calories, and more!

How do you gain weight if you’re skinny?

You gain weight by eating more food – increasing your calorie intake so that it’s above your ‘maintenance calories’. Simply eating more than you use is all it takes, and weight loss is the opposite (eating less than you need).

Skinny guys and hardgainers just need to drastically increase their food intake. There’s no way around the calorie math – you just need to put time into the estimate of your calorie needs, and then focus on eating more calorie dense foods – boosting your calorie intake per week.

There’s no trick to this. Consistency is important and you just need to gain weight slowly – don’t expect too much too soon. Play the long game and plan on gaining weight for the next year.

How to gain weight fast?

You can gain weight fast by eating a lot more – but that does mean that you’re likely to gain a lot of body fat. Excess calories are stored as fat because your body can only gain so much muscle mass at once, and anything above that amount is put in ‘storage’ as body fat.

You can gain as much weight as you want quickly, but it won’t be a healthy weight and your body fat percentage will be the main thing that increases. This carries the increased risk factors for disease and poor health you’d expect!

How many calories should I eat to gain muscle?

Around 500 calories more than your TDEE – and you can do this by eating more often, eating calorie dense foods, or just increasing your meals-per-day.

You can use a larger caloric surplus if you’re bigger or more active, up to around 750/800 calories. Any more than this is typically wasted and causes body fat accumulation without any real benefits.

Is it normal to gain weight in one day?

Yes – you will experience both weight gain and weight loss within one day as your body composition isn’t stable. You’ll gain and lose water weight, carbohydrate storage, intestinal mass, and you’ll excrete or breathe out significant amounts of weight.

Your body weight varies around a mostly-stable number that we call your ‘dry mass’ which means the physical tissues of the body. Things in those tissues like water and glycogen can change body weight quickly, but this doesn’t reflect muscle gain or fat loss in the short term.

Can you gain muscle mass and burn fat at the same time?

Yes – this is called recompositioning, because you’re changing your body composition without weight gain or weight loss. It’s easy for beginners and becomes harder every year you gain experience with lifting weights or dieting for body composition.

You have to eat a very small calorie deficit and high protein diet, as well as plenty of vitamins and minerals. It’s a good way to change your body but does demand a lot of discipline and planning!

How many calories in a pound of fat?

A pound of fat is estimated to be “worth” around 3500 calories, though this does depend on the kind of fat that’s stored and the efficiency of the body. Body fat has – on average – a 3500 calorie content.

This means the average person contains 10,000s to 100,000s of calories. You shouldn’t eat one, though, that’s excessive calorie intake.

How many calories in a pound of muscle?

Estimates put a pound of muscle at around 700 calories in a pound of muscle due to the significantly lighter and denser compounds in muscles. This pound of muscle is smaller than a pound of fat, and is actually very metabolically active – and requires around 2000 calories of surplus to build.

This makes muscle a complicated organ and one of the most important and interesting tissues. It’s key for keeping your metabolism and joints healthy, too!

Is muscle really heavier than fat?

Yes – muscle is heavier than fat when compared on the same amount of volume (space they take up). A cubic metre of muscle is far heavier than a cubic metre of fat due to the tightly packed structure and the extra weight that comes from the liquids stored in muscle.

Fats also contain liquids but the cells are typically wider spaced and have a less dense structure.

Does Strength Training Burn Fat?

Yes – lifting weights or performing bodyweight exercises burns calories – they’re required to repair muscle tissue and replace the high-energy fuel in muscles. These are also calculated after exercise – where the calorie-burning effects of strength training last for 36-48 hours.

This is why weight training is one of the most consistent ways to burn fat. It’s also a great way to protect lean body mass during a weight loss diet – where using muscles stops your body from burning them up for energy!


You need to eat around 500 calories more than you use per day to gain weight, specifically gain muscle mass, and improve your health. This is the healthy way to gain weight and the slower you go, the better the health and performance factors, even if your weight gain is a little slower.

Focus on quality, and not just quantity, bringing your best effort for diet with a small calorie surplus, lots of high quality proteins, and replacing processed foods with fruit, veg, whole grains, lean meats, seafood, and healthy fats.


If you know that you need to gain weight for your fitness goals, it’s just about putting things in the right order and right intensity to keep body fat down and build lean muscle mass!



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