How many extra calories do I need to eat each day to gain weight?

It depends on your body and how fast you want to gain. A common starting point is 250 to 500 extra calories per day above your maintenance level (TDEE). This calculator figures out your exact surplus based on your age, height, weight, activity level, and chosen pace of gain.

What formulas does this calculator use?

It uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR). If you enter your body fat percentage, it also uses the Katch-McArdle equation and averages the two for a more accurate result. Your BMR is then multiplied by an activity factor to get your Total Daily Energy Expenditure (TDEE).

Is it better to gain weight slowly or quickly?

For most people, slow to moderate gain (0.25 to 0.5 pounds per week) is better. A slower pace means more of the weight you add is muscle instead of fat, especially if you are strength training. Fast gain (1+ lb/week) gets you to your goal sooner but usually adds more body fat.

How much protein should I eat when trying to gain weight?

This calculator sets protein at about 0.9 grams per pound of your target body weight. That amount supports muscle growth without going overboard. The rest of your calories come from carbohydrates and fat.

What if I don't know my body fat percentage?

That's fine. Leave the body fat field blank and the calculator will estimate it for you using your age, sex, height, and weight. The estimate uses a formula based on BMI. For a more precise number, you can measure it with calipers, a DEXA scan, or a body fat scale.

Can women use this weight gain calculator?

Yes. The calculator adjusts its formulas based on whether you select male or female. Women typically have a lower BMR than men of the same size, so the calorie targets will be different.

TDEE stands for Total Daily Energy Expenditure . It is the total number of calories your body burns in a full day, including basic body functions, daily movement, and exercise. To gain weight, you need to eat more calories than your TDEE.

BMR stands for Basal Metabolic Rate . It is the number of calories your body burns at complete rest just to keep you alive — things like breathing, pumping blood, and keeping your organs running. Your TDEE is your BMR multiplied by an activity factor.

Why does the calculator show my BMI changing?

BMI is calculated from your weight and height. As your weight goes up, your BMI goes up too. The calculator shows your current BMI and what it will be when you reach your goal weight so you can make sure you stay in a healthy range.

What is FFMI and why is it shown?

FFMI stands for Fat-Free Mass Index . It measures how much lean mass (muscle, bone, organs) you carry relative to your height. It helps you see how muscular you are compared to natural limits. A higher FFMI means you carry more lean tissue for your size.

How accurate is the week-by-week projection?

The projection is an estimate based on a steady calorie surplus and consistent activity level. In real life, weight gain is not perfectly linear. Water weight, stress, sleep, and workout changes can cause small ups and downs from week to week. Use the table as a guide, not an exact prediction.

What activity level should I choose?

Pick the option that best matches your typical week. If you sit most of the day and rarely exercise, choose Sedentary . If you work out 3 to 5 days a week, Moderately Active fits most people. Picking a level that is too high will give you a calorie target that is too large, which could lead to extra fat gain.

Can I use this calculator if I want to lose weight instead?

This tool is designed for weight gain. If you set a target weight lower than your current weight, it will calculate a calorie deficit instead. However, for a better experience with weight loss goals, a dedicated weight loss calculator would give you more relevant guidance.

Why is my daily calorie number never below 1,200?

The calculator has a safety floor of 1,200 calories per day. Eating fewer than 1,200 calories can deprive your body of essential nutrients and is generally considered unsafe without medical supervision.

How does the custom pace option work?

When you select Custom under Weight Gain Pace, a new field appears where you can type in your own weekly gain rate in pounds or kilograms. The calculator then uses that number to figure out the exact daily calorie surplus you need.

Do I need to eat the same number of calories every day?

You don't have to hit the exact same number every single day. What matters most is your weekly average . If you eat a little less on one day, you can make up for it the next day. Staying consistent over the week is what drives steady weight gain.

Why does the macronutrient breakdown show 25% fat?

The calculator sets fat at 25% of total calories because that amount supports hormone health and vitamin absorption while leaving enough room for protein and carbs. Fat has 9 calories per gram, so even at 25% it provides a solid amount of energy.

What does the body composition bar show?

The bar shows the estimated split between your fat mass and lean mass based on your current weight and body fat percentage. The orange/red portion is fat and the green/purple portion is lean tissue like muscle and bone.

Weight Gain Calculator - Plan Your Goals

Introduction

Gaining weight in a healthy way takes more than just eating extra food. You need to know how many calories to eat each day, what foods to focus on, and how long it will take to reach your goal. Without a clear plan, you might gain too much fat or not see any progress at all.

This Weight Gain Calculator builds a complete plan based on your body and lifestyle. Enter your age, height, current weight, and goal weight, then choose your activity level and how fast you want to gain. The calculator uses proven formulas like the Mifflin-St Jeor and Katch-McArdle equations to find your maintenance calories and the exact surplus you need. It also gives you a suggested macronutrient breakdown showing how many grams of protein, carbs, and fat to eat each day. You'll see your BMR, TDEE, current and goal BMI, body composition estimates, and a week-by-week projection chart that tracks your progress from start to finish.

How to Use Our Weight Gain Calculator

Enter your personal details, activity level, and weight goal below. The calculator will tell you how many calories to eat each day, give you a macronutrient breakdown, and show a week-by-week plan to reach your target weight.

Sex: Select whether you are male or female. This affects how your body burns calories at rest, so picking the right option helps the calculator give you an accurate calorie target.

Age: Enter your age in years (between 15 and 80). Your age plays a role in your metabolism, which changes how many calories your body needs each day.

Unit System: Choose between Imperial (pounds and feet) or Metric (kilograms and centimeters). The calculator will convert your numbers if you switch between the two.

Height: Enter your height in feet and inches (Imperial) or centimeters (Metric). Your height is used to figure out your basal metabolic rate and BMI. If you're curious about predicting future growth, try our Height Calculator.

Current Weight: Enter how much you weigh right now in pounds or kilograms. This is the starting point the calculator uses to build your weight gain plan.

Body Fat % (Optional): If you know your body fat percentage, type it in here. If you leave it blank, the calculator will estimate it for you based on your other measurements. This helps provide a more detailed body composition breakdown. You can get a more precise reading using our Body Fat Calculator.

Activity Level: Pick the option that best matches how active you are each day. Choices range from Sedentary (little or no exercise) to Extra Active (very hard exercise or a physical job). This determines how many calories you burn on top of your base metabolism.

Target Weight: Enter the weight you want to reach in pounds or kilograms. This must be different from your current weight so the calculator can map out a plan for you. Not sure what a healthy target looks like? Our Ideal Body Weight Calculator can help you find a reasonable range.

Timeframe: Enter how many weeks you want to spend reaching your goal (between 1 and 260 weeks). This helps the calculator show you a realistic week-by-week projection.

Weight Gain Pace: Choose how fast you want to gain weight. Slow (~0.25 lb/week) keeps fat gain low, Moderate (~0.5 lb/week) offers a balanced approach, and Fast (~1.0 lb/week) is a more aggressive bulk. You can also pick Custom to set your own weekly rate.

What Is Weight Gain and Why Does It Matter?

Weight gain means increasing your total body weight over time, usually by eating more calories than your body burns each day. While many people focus on losing weight, there are plenty of reasons someone might need to gain weight. Athletes may want to build muscle and get stronger. People recovering from illness or surgery might need to restore lost weight. Some individuals are naturally underweight and want to reach a healthier size. Whatever the reason, gaining weight the right way takes a clear plan.

How Weight Gain Works: The Calorie Surplus

Your body burns a certain number of calories each day just to stay alive and do its normal activities. This is called your Total Daily Energy Expenditure (TDEE). To gain weight, you need to eat more calories than your TDEE. This extra amount is called a caloric surplus. A general rule is that about 3,500 extra calories equals roughly one pound of body weight gained. So if you eat 500 extra calories per day above your TDEE, you could expect to gain about one pound per week. You can find your exact TDEE using our TDEE Calculator.

Your TDEE depends on several things:

Basal Metabolic Rate (BMR) — the calories your body burns at complete rest just to keep your heart beating, lungs breathing, and organs working. Use our BMR Calculator to find yours.
Activity level — how much you move and exercise during the day
Age, sex, height, and current weight — all of these affect how many calories you burn

Slow vs. Fast Weight Gain

Not all weight gain is the same. How fast you gain matters a lot. Gaining weight slowly (about 0.25 to 0.5 pounds per week) tends to result in more lean muscle and less body fat, especially when combined with strength training. Gaining weight quickly (1 pound or more per week) will get you to your goal faster, but a larger portion of that new weight is likely to be stored as fat rather than muscle. For most people, a moderate pace is the best balance between speed and quality of weight gained.

The Role of Macronutrients

Calories tell you how much to eat, but macronutrients tell you what to eat. For a detailed personalized breakdown, try our Macro Calculator. The three macronutrients are:

Protein — essential for building and repairing muscle. When gaining weight, eating enough protein (roughly 0.8 to 1 gram per pound of your target body weight) helps ensure that more of your weight gain comes from muscle instead of just fat. Our Protein Calculator can help you dial in your exact daily protein needs.
Carbohydrates — your body's main source of energy. Carbs fuel your workouts and daily activities, and they make it easier to reach a calorie surplus because many carb-rich foods are calorie-dense. Use our Carb Calculator to figure out how many grams to target each day.
Fat — important for hormones, brain health, and absorbing certain vitamins. Fat has 9 calories per gram (compared to 4 for protein and carbs), so it is a very efficient way to add calories to your diet.

Body Composition: Muscle vs. Fat

When you gain weight, your body adds a mix of muscle and fat. Your body fat percentage tells you what share of your total weight is fat versus lean tissue like muscle, bone, and organs. Knowing this number helps you set smarter goals. For example, someone with a low body fat percentage might focus on a larger surplus and faster gain, while someone with a higher body fat percentage might choose a slower approach to limit additional fat storage. You can track your lean tissue with our Lean Body Weight Calculator.

The Fat-Free Mass Index (FFMI) is another useful number. It measures how much lean mass you carry relative to your height. It helps you understand where you stand compared to natural muscular potential. Check yours with the FFMI Calculator.

BMI and Weight Gain

Body Mass Index (BMI) is a simple number calculated from your weight and height. While it does not tell the difference between muscle and fat, it gives a general idea of whether your weight falls in an underweight, normal, overweight, or obese range. Tracking how your BMI changes as you gain weight can help you stay within a healthy zone. Other useful proportional metrics include the Waist to Hip Ratio Calculator and the Waist to Height Ratio Calculator.

Tips for Healthy Weight Gain

Eat consistently. Aim for three full meals and two to three snacks per day. Skipping meals makes it hard to hit your calorie target. Our Calorie Calculator can help you figure out exactly how many calories you need.
Choose nutrient-dense foods. Focus on whole grains, lean meats, eggs, dairy, nuts, seeds, avocados, and healthy oils rather than junk food. Make sure you're getting enough fiber and staying properly hydrated as you increase your food intake.
Strength train regularly. Lifting weights signals your body to build muscle with those extra calories instead of only storing fat. Tools like the 1RM Calculator and RPE Calculator can help you structure your training.
Be patient. Healthy weight gain is a gradual process. Gaining 0.5 to 1 pound per week is realistic and sustainable for most people.
Track your progress. Weigh yourself at the same time each week and adjust your calories if your weight is not moving in the right direction. You can also monitor how many calories you burn through exercise to keep your surplus on target.
Talk to a doctor. If you are underweight or have a medical condition, get professional guidance before starting a weight gain plan. Expectant mothers looking for guidance should use our Pregnancy Weight Gain Calculator instead. If your goal is to lose weight rather than gain, our Weight Loss Calculator is a better fit.

Weight Gain Calculator

Your Weight Gain Plan