Weight Loss Calculator

The weight loss calculator will determine your daily calorie needs based on your body data and goals. It estimates your energy expenditure then deducts a safe calorie deficit to make the number on the scale go down at the pace you choose. Enter your age, height, weight, activity level, add a goal and the calculator will give you the daily calorie intake that you should be aiming for.

This is how the calculator works:

Weight change ultimately depends on energy balance. When you take in fewer calories than you expend, your body taps into reserves, leading to weight loss. The calculator figures out this difference in three steps.

First it estimates your Basal Metabolic Rate (BMR), which is the amount of energy your body uses at rest. It then multiplies this value by an activity factor to get your total daily energy expenditure, i.e. how many calories you burn in a normal day. Finally it subtracts an appropriate calorie deficit based on your goal and displays your recommended daily caloric intake to help you achieve your goal.

You can create your plan in two ways. Select a weekly weight loss and the calculator will tell you how long it will take to reach your goal; or select a target date and it will calculate the weekly rate and calorie deficit that you need to achieve.

Basic turnover formula:

The base metabolism makes up the largest part of your calorie burn, so this formula is important. This tool offers three formulas, with the default being the one most studies have confirmed to be the most accurate.

Mifflin St. Jeor (standard)

This formula was published in 1990 and is currently the standard for healthy adults. The weight should be given in kilograms, the height in centimeters, and the age in years.

Revised Harris-Benedict Formula

This is a revised version of the original 1918 formula that was published in 1984. It's slightly older but still commonly used today.

Katch-McArdle

It uses lean body mass instead of gender and can therefore be the most accurate if you know your body fat percentage. Here F is for body fat as a decimal with 1 being the base.

From basic turnover rate to daily target.

Your total daily energy expenditure is your basal metabolic rate multiplied by an activity factor: for a mostly sedentary day this will be 1.2, while very intense training sessions can have a factor of about 1.9 or higher.

To lose weight you need to take in fewer calories than this amount. About one kilogram of body fat stores 7,700 calories while a pound stores about 3,500 calories. To safely lose half a kilo per week, a deficit of around 550 calories per day is required, whereas to lose a pound (about 450 grams) you need roughly 500 fewer calories.

Activity level overview:

The activity factor covers all activities except rest. So pick the row that matches your typical week and not one that reflects your best form.

How fast is safe?

For most people, losing about half a kilogram to one kilogram, or one to two pounds, per week is reasonable.

Health authorities also set minimum calorie levels. Most guidelines recommend that women should not eat fewer than 1200 calories and men should not eat fewer than 1500 unless under medical supervision. If your goal is lower, the calculator will warn you and you should slow down your weight loss.

Proteins, carbohydrates and fats

The total number of calories determines whether you lose weight or not but the ratio of protein, carbohydrates and fats affects your well-being and how much muscle mass you can gain. The calculator shows a balanced initial ratio: 30% protein, 40% carbohydrates and 30% fat; proteins and carbohydrates are counted with 4 calories per gram while fats are counted with 9 calories per gram. Many people who do strength training increase the amount of protein to almost one gram per pound of body weight then adjust the ratio of other nutrients according to their personal preferences.

When the number on the scale is stagnant

Weight loss is rarely a straight line. After you lose weight your calorie burn will decrease so an initial effective calorie deficit may gradually become less effective. Re-calculate and adjust every few pounds. Some people also vary their calories, eating more on active days and less on rest days to allow for flexibility while still hitting the same weekly total.