You want to gain weight to improve the way you feel, look and perform athletically. Weight gain happens when you create a calorie surplus. Figure out how many calories you need daily to maintain your weight and then add 250 to 500 calories to that number to get your new daily goal. Eating that many calories each day will result in a safe, manageable 1/2 to 1 pound of weight gain per week.

Figure Out Your Maintenance Calories

An online calculator can help you determine how many calories you need daily to maintain your present weight. Alternatively, speak to a dietitian. The maintenance number will take into account your age, gender, size and activity level. Young, active men usually need more calories to maintain their weight than older, sedentary women. For example, a 48-year-old woman who stands 5 feet, 4 inches and weighs 100 pounds, who is active less than an hour per day, needs at least 1,800 calories to simply maintain her size. A 30-year-old man who stands 5 feet, 11 inches and weighs 130 pounds, and is active more than an hour on most days needs 3,205 to maintain his weight.

Weight Gain Strategies

To the number of calories you found you need to maintain your weight, add 250 to 500 to come up with how many you need daily need for weight gain. If you find it hard to gain weight, it's likely you have a faster-than-average metabolism. The number you arrive at with calculations may then be slightly below your daily needs. If, after a few weeks, you aren't measurably adding pounds -- add another 100 to 250 calories per day to bring about weight gain results.

Divide your total calories into three larger meals and two or three smaller snacks. For example, for a man who needs to eat 3,000 calories daily, aim for three meals of 750 calories each and two snacks of 375 calories each. Or, for a woman who needs to eat 2,200 calories, she could eat three meals of 600 calories each plus two 200-calorie snacks.

Eating increased portion sizes of healthy foods at meals will help you hit your calorie goals. Counting calories will also help you identify calorie-dense foods so you eat enough to gain weight. For example, a cup of nuts that provides you with 886 calories or a cup of dried apricots with 313 calories is a preferable snack to a cup of air-popped popcorn with just 31 calories.

Keep a Record to Manage Your Weight

The way you choose to record your meals' calorie content depends on what's most convenient for you. Many online programs and apps for your smart phone allow you to keep track virtually. These programs usually have nutrition information readily available, so you don' t have to research foods or read nutrition labels. A notebook might be easier for you to transport during the day and you can transcribe it later in the evening to an online program that makes tallying simple.

Determine portion sizes to get an accurate calorie count and make sure you're not undereating 1. A food scale and measuring cups and spoons are the most accurate ways to measure, but they're not always convenient or practical. You can eyeball portion sizes using common reference points instead. A 1/2 cup of grains is about the size of your fist, a 3-ounce portion of meat or poultry is approximately the size of a bar of soap, a 3-ounce fillet of fish looks like a checkbook, a teaspoon of oil is equal to the tip of your thumb and a 2-tablespoon portion of nut butter looks like a ping-pong ball.

Tracking your calorie intake also helps you identify if and why you're missing meals. A skipped meal means you're missing an opportunity to take in extra calories and achieve your calorie surplus. In your food journal, write a small note as to why you missed a particular meal or went for several hours without a snack. This can help you learn how to deal with such setbacks -- including packing healthy, portable foods such as granola or setting a phone alarm to remind you that it's snack time.

Track Calories Burned Through Exercise

Resistance training is essential for healthy weight gain. Do at least two sessions per week that address every major muscle group. Use heavy weights for a minimum of one set of four to eight repetitions. A general weight training session burns about 90 calories for a 125-pound person and 112 calories for a 155-pound person. Account for this activity when determining your calorie needs.

A post-resistance training snack that includes a serving of protein supports muscle gain. Options include whey protein blended with milk and a banana, chicken breast with a sweet potato or Greek yogurt with granola.