You can use the Diet Calculator to assist with calculations. but you should still read this page to learn about various calorie deficits, and what goes into determining appropriate calorie intakes.
All numbers (whether from the calculator or doing it by hand) are simply estimates. Calorie calculations can easily be "off" by 200 - 300 calories or possibly more. You always have to be ready to adjust your diet according to real world changes (are you gaining weight, losing, or staying the same). However, this gives you a starting point, which is better than nothing.
You may not actually need to calculate calories at all — depending on the methods and tools you are using. For example, some people prefer to keep track of "macros" (grams of carbs, protein and/or fat) instead of calories (the Diet Calculator figures out your macros, too). Other methods don't require any calorie counting.

Calorie counting is a debated topic. In the end, it's a personal decision. However, even if you don't strictly calorie count everything, having some kind of ballpark number in your head can help you make decisions. And it helps put things in perspective. When you do add up calories in a meal, you'll know roughly what that means to your total intake.

Simple Estimation Method

If you want a "quick and dirty" way to estimate calorie intake targets, try the following. We still suggest doing the more detailed (standard) calculation below or using the Diet Calculator for more accurate results.

For Maintaining Weight

Multiply your weight by the following:

Sedentary: 10 for women, 11 for men
Lightly Active: 11 for women, 12 for men
Moderately Active: 12 for women, 13 for men
Very Active: 14 for women, 15 for men
Extremely Active: 18 for women, 19 for men

The numbers above are "calories per pound" of bodyweight, so multiplying by your bodyweight gives you your total calories for the day.

NOTE: Sedentary means you get little activity except sitting at a desk or light household tasks. Lightly Active means you some some low-intensity aerobic/cardio type exercise (walking, jogging). Moderate activity means you get higher-intensity aerobic activity (sprints, HIIT, etc) or weight training. Very Active means you get both weight training and aerobics, roughly 3 - 5 times per week. Extremely Active means you are an athlete in training (like 2 or more hours per day of training).

For Weight Loss

A good starting point for sustainable weight loss over a long period of time (when done as part of lifestyle healthy eating changes) is to multiply your weight by 10 - 12 calories per pound. Many people simply start with 12 and if weight loss isn't happening after 2 - 3 weeks then adjust downward by 50 - 100 calories.

In general you want to "aim high" so that you are eating as much food as possible while still losing weight. This potentially allows you to hit a sweet spot where you lose weight gradually while getting the least resistance from your body in terms of metabolic adaptation, hunger and cravings. This calorie range generally works out to be 15-20% deficit, which is a Small to Moderate range as described below that may give 1/2 lb to 1 lb per week loss. Again, this is a longer-term, conservative approach and is best combined with healthy lifestyle changes in diet and activity levels.

Standard Calculation Method

What we are calculating here is what we call "maintenance calories", the caloric intake that will maintain your current weight (aside from normal weight fluctuations of 2 - 5 pounds). It's an estimate of how many calories your body burns per day on average. If you can aim to get roughly that many calories per day (or at least, not exceed it) then you should be able to maintain your weight.

Maintenance calories is the same thing as the "Energy Out" side of the equation, or Total Energy Expenditure (TEE), in Energy Balance Equation.

TEE = RMR + TEF + PE + NEAT (please refer to Energy Balance Equation for details)

RMR:

Use the Mifflin St Jeor Equation:

Women: (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
Men: (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5

Or if you want a quick rough estimate:

Multiply your weight (pounds) by:
10 calories per pound if you are female
11 calories per pound if you are male.

TEF:

Multiply the above by 1.1

PE:

Multiply the above by:

0.9 if you get no formal exercise, and you sit most of the day (desk job, TV, computer, couch)
1.1 if you get very little (a few easy walks a few times per week)
1.3 if you do moderate exercise 3-5 days per week for 45-60 minutes each time
1.5 if you do moderate exercise 5-7 days per week for 45-60 minutes each time
1.7 to 2.0 if you are a training athlete (hard/serious or long bouts of exercise almost daily)

NEAT:

Ignore (varies too much; hard to predict)

Example: 150 pound female, moderate exercise

RMR: 150 x 10 = 1500 calories per day
TEF: 1500 x 1.1 = 1650 calories per day
PE: 1650 x 1.3 = 2145 calories per day

Lose Weight (Calorie Deficit)

According to the Energy Balance Principle, to lose weight you will need to create a calorie deficit -- where your calorie expenditure is greater than the amount of calories you are consuming.

You do this by first estimating your maintenance level calories as described above. Then you lower your food intake by a certain percentage.

The calculations below are based on the fact that each pound of fat contains 3500 calories. So you have to burn through 3500 calories of fat storage to lose 1 pound of fat.

First a note about expectations:

Again these are just estimates. Be prepared to adjust.
Weight and gender can influence rates of loss. Some women may actually lose a little slower than expected. And if you are very large with a lot of fat to lose, you may lose faster than expected.
Water weight can mask true fat loss.
Metabolic adaptations can slow results.

Here are a few weight loss guidelines:

Small: 10% (multiply maintenance by 0.9)
Moderate: 15% to 25% (multiply maintenance by 0.85 to 0.75)
Aggressive: 30% to 50% or more (multiply maintenance by 0.7 to 0.5, or lower)

Small Calorie Deficit

Expectation: Around 0.5 to 0.8 pounds per week, if there is a 200 to 400 calorie per day deficit
Example: 2145 calories x 0.9 = 1930 calories, a 215 calorie deficit

The benefit of a small deficit (below 15%) is that dietary changes you make are small and feel easy. However, it's hard to do by "counting calories" because you have to be very meticulous (or obsessed) about monitoring every calorie. A little mis-measurement can mean you are no longer in a deficit. Or, what appears to be a 200 calorie deficit turns into only 50 calories. Which of course means weight loss doesn't happen or is too slow.

Unless you are a meticulous and dedicated calorie-counter, the best way to implement a small deficit is to make relatively small changes your habits and food choices -- changes you can easily handle and may hardly even notice. This membership site contains a lot of tools you can use for this.

It may actually be more helpful to think of these small, easy changes as a way to control your weight. Then, if you lose weight, great! If you don't lose, at least you avoid gaining weight. Either way it's a winning strategy you can do for a long time, even a lifetime.

Moderate Calorie Deficit

Expectation: Around 0.8 to 1.5 pounds per week, if there is a 400 to 700 calorie per day deficit
Example, using 80%: 2145 calories x 0.8 = 1715 calories, a 430 calorie deficit

A 20% deficit is a common recommendation. This approach usually means you need to make significant changes to your diet, which means it "feels like a diet" while still being something you can do for quite a while. This is a better choice if you want to see noticeable results a little more quickly than the rather easy/lifestyle changes mentioned above.

This kind of calorie deficit is harder to mess up because you are eliminating a bigger chunk of overall calories. Even if you miscalculate something, it's not likely that you will entirely eliminate the deficit.

You'll want to be monitoring or at least eyeballing your caloric intake to keep yourself on track.

Metabolically, as with any weight loss, your body will resist to some degree but not nearly as much as more aggressive levels. After awhile (especially if you nearing your ideal weight or are getting more lean) you will want to establish regular diet breaks and possibly re-feeds.

Aggressive Calorie Deficit

Expectation: Around 2 pounds per week, assuming a 1000 calorie per day deficit
Example, using 50%: 2145 calories x 0.5 = 1070 calories (rounded), a 1070 calorie deficit

On the lower end, say 30% deficit, it's not a lot different from a "moderate" approach. Just a little more calorie restriction.

As you cut more and more calories, your weight loss becomes more dramatic. If you want maximum weight loss, it's what you have to do. It involves a more strict diet and a more carefully planned strategy.

These more aggressive approaches are what our rapid weight loss protocols are all about.

There's some controversy and misunderstandings regarding "fast weight loss" diets. You can read more about it here, to find out if it's an approach you'd like to try.

Should You Set Ideal Weight Targets?

It might be tempting to calculate your calorie deficit based on your target or ideal goal weight (current maintenance minus target maintenance). That's not a good idea because it doesn't mean anything (it's the wrong kind of math). Instead, do what we've shown you above: figure out roughly how much you want to lose per day (or better, per week) and adjust accordingly. You can then project how long it will take to reach your goal weight. Just keep in mind that timeline will change.

What About Exercise (Energy Expenditure)?

Your diet makes the greatest impact on your weight loss, so that's why we focus on reducing calories in your diet. However, energy expenditure DOES count. You should consider it as part of a Small or Moderate weight loss strategy -- or especially during maintenance. Exercise during Aggressive weight loss should be done in moderation, or sometimes not at all. But it all depends on the person. We discuss all this more in the Exercise section.