Weight Loss Calculator

What’s Your Optimal Caloric Intake?

With Lifespan’s weight loss calculator, you can accurately determine the optimal calories you need to intake daily to reach your target weight. Not only can this calculator guide you to your target weight, it can lead you towards reaching your optimal body composition over time.

Understanding The
Impact Of Diet And Exercise

Step 1: Your Profile


  • Age


  • 65

  • Lifestyle

  • Current Weight


  • Goal Weight


  • 21.6

Step 2: Getting There

How hard do you want to work?

Days needed to acheive weight loss:

Step 3: Diet and Exercise

Select the balance between diet and exercise:



The number of calories to take out of your diet each day:

Plus, the number of minutes you need to exercise each day:

Moderate Intensity

Vigorous Intensity

View your detailed weight loss projection plan

This calculator assumes you're not currently gaining or losing weight, and that you're not doing any special exercise.

Products to help you reach your goals

Your Detailed Weight Loss Plan

Three examples for removing the recommended amount of daily calories from your diet:

fewer oatmeal cookies
4 fewer oatmeal
fewer glasses of beer or wine
2 fewer glasses
of beer or wine
fewer chicken legs and thighs
2 fewer chicken legs
and thighs

Two examples for meeting your recommended minutes of exercise

3.2 miles brisk walking
3.2 miles brisk walking
2.2 miles jogging or running
2.2 miles jogging or running

Lifespan Fitness’s weight loss calculator uses models developed by national health institutes. You can utilize it for both weight loss and weight gain goals. Unless you are under the age of 18 or currently pregnant or breastfeeding, our weight loss calculator can help you better assess your fitness goals.

The only people who should use the weight loss calculator are those over 18 years old who are not pregnant or breastfeeding.

If you’re ready to start losing weight the right way, it’s time to incorporate tools that simplify your process. That’s why we created our weight loss calculator; we want you to enjoy your path to health and well-being.

What Are Calories?

A calorie is a unit that measures energy. To lose weight, you must burn more calories than you intake. To gain weight, you need to consume more calories than you burn.

How to Reduce Calories
eat more protein
Eat More Protein

Increasing your protein is an easy way to limit your calories because it contains less calories per g than fat. You consume more calories with fat than you do with protein. Protein can also help battle cravings. Some research shows high protein snacks can help enhance feelings of fullness and decrease your feelings of hunger. Other studies also show the benefits of protein for building muscle mass. You can increase your protein by eating more eggs, meat, poultry, tofu, nuts, seeds, and legumes.

limit sugary drinks
Limit Sugary Drinks

Another easy way to limit your calories is to reduce sugar consumption. Many beverages have high concentrations of sugar, such as juice, soda, and alcoholic beverages. Your brain doesn’t register liquid calories as quickly as it does solid calories obtained from food. Therefore, these calories affect your feelings of hunger and fullness less significantly. Studies have also shown a correlation between drinking sugary drinks and obesity.

drink more water
Drink More Water

The more water you drink, the less calories you’ll consume. However, drinking more water can be more difficult than you might anticipate. Despite it sometimes feeling like a chore, adequate hydration is associated with improved brain health and weight management, as well as a reduced risk of kidney stone risk. Drinking water can immediately reduce feelings of hunger, causing you to eat fewer calories.


Too much caloric restriction can slow your metabolic rate and cause you to feel an increase in appetite. It can also lead to muscle loss and hurt your health rather than help it. Resistance training activities such as weightlifting have been shown to reduce muscle loss, which can keep your basal metabolic rate high, improving both the quality and quantity of your weight loss. If you can’t get to a gym, you should consider doing bodyweight exercises, such as pushups, situps, and squats.

There is lots of advice out there on how to cut calories. We've found one of the clearest and widely agreed-to sources of information is from the Centers for Disease Control (CDC), the official health organization of the United States. Start with their article on Cutting Calories.

Starting an exercise program is simpler, but there are still some useful guidelines. Try the CDC's
Physical Activity for a Healthy Weight.

How The Weight Loss
Calculator Works
The Science Behind Calculating Weight Loss

While losing weight involves many variables that change from person to person, there is still a core science that can be the basis behind planning a weight loss strategy. The widely-accepted science behind the weight loss calculator is:

  • One pound of mostly-fat body weight is the equivalent of 3,500 calories of either food or exercise.
  • The appropriate amount of calories to cut from your diet is between 20% and 40% of your normal calorie requirement. See the CDC.
  • Moderate exercise is considered to be 4.5 METs. (A MET is a rate of energy expenditure, similar to watts.) Vigorous exercise is 7 METs. Calorie consumption is: 1 calorie (technically, kilocalorie) per kilogram body weight per hour per MET.

When your body burns fat, 84 percent of it turns to carbon dioxide that your lungs exhale out of your body. The remaining 16 percent becomes water that you either secrete through your skin via sweat, or excrete via urine.

The water weight you lose while dieting is released in the form of glycogen. Low glucose levels in the blood during dieting can cause the release of some of your needed glucose. This glucose is primarily stored in the liver and the muscles. Each gram of glycogen is bound to three or four grams of water and you excrete your glycogen during the initial stages of dieting, causing temporary weight loss.

Your body fat percentage is another metric you can use to determine your ideal weight. You shouldn't base your overall health on your weight alone. Calculating your body fat content can help you determine your weight because it accounts for your muscle mass.

To achieve healthy and sustainable weight loss, you should not lose more than two lbs of fat per week. Taking this into account, the average person would have to reach a caloric deficit of 1,000 calories per week. However, it’s important to note that everyone has different basal metabolic rates. You should consider your BMR when trying to decide your total caloric intake. If you lose more than 2 lbs per week, you are likely losing predominantly water weight. Your goal should be to lose 1-2 lbs per week. It’s also important to remember that combining a small caloric deficit with exercise is the best way to maximize your weight loss while ensuring your overall health.

limitations of body weight color coding
Limitations of Body Weight
Color Coding

The math behind the body weight color coding, something called Body Mass Index (BMI), is applicable and useful for about 95% of the population. It is not useful for highly fit people (who won't be using this calculator anyway). It is also not useful for very tall people. Use the color coding as a guideline for evaluating your body weight. Don't use it as a medical diagnosis.

Calorie Reduction

This is a reduction compared to your estimated nominal calorie consumption, meaning the amount of calories you consume while staying the same weight. If you are currently gaining weight, you need to reduce your calories even further.

Keeping track of how many calories you consume is not easy. WebMD has a good food calorie list.

Examples of Moderate
Intensity Exercise
  • Walking briskly (around 3 miles per hour)
  • Water aerobics
  • Bicycling 6 to 10 miles per hour
  • Tennis (doubles)
  • Ballroom dancing
  • General gardening
Examples of Vigorous
Intensity Exercise
  • Jogging or running
  • Hiking uphill or with a heavy backpack
  • Jumping rope
  • Tennis (singles)
  • Aerobic dancing
  • Heavy gardening (continuous digging or hoeing)
  • Bicycling 10 miles per hour or faster
  • Non-casual swimming laps