How Many Calories to Eat to Lose Weight, Worked Out Step by Step

Every calorie calculator gives you a number, but few explain where it comes from or what to do when it turns out to be wrong. That matters, because two calculators can disagree by a few hundred calories for the same person.

The method is simpler than it looks. You estimate how much you burn at rest, add your daily activity, subtract a sensible amount for weight loss and make sure the result stays above a safe minimum. Then the scale tells you whether the estimate was right.

This guide walks through each step with a worked example, shows three sample results and explains why your number needs updating as you lose weight.

Step 1: Estimate Your Resting Burn

Your basal metabolic rate, or BMR, is the energy your body uses at rest to breathe, circulate blood and keep its organs running. For most people it makes up the largest share of the calories they burn each day.

The standard way to estimate it is the Mifflin-St Jeor equation, published in a 1990 study of 498 adults. It uses weight in kilograms and height in centimeters:

• Women: 10 × weight + 6.25 × height − 5 × age − 161
• Men: 10 × weight + 6.25 × height − 5 × age + 5

To convert, divide pounds by 2.2 and multiply inches by 2.54. Take a 35-year-old woman who is 5 feet 4 inches (163 cm) and 170 pounds (77 kg). Her estimated resting burn comes to about 1,450 calories a day.

No formula is exact for every person. A systematic review found Mifflin-St Jeor was the most reliable of the common equations, landing within 10% of measured resting burn for more people than any other. The same 2005 review also warned that individual errors can still be large, which is why testing your number later matters.

Step 2: Add Your Daily Activity

Next, multiply your resting burn by an activity factor. The result is your total daily energy expenditure, or TDEE, which is roughly your maintenance number. It’s the amount you could eat each day without gaining or losing weight.

The labels on activity levels are vague, so daily steps make them easier to judge. The step ranges below follow the categories proposed in a 2004 pedometer review, which classed under 5,000 steps a day as sedentary.

The example woman walks about 6,000 steps a day, so she uses the lightly active factor: 1,450 × 1.375 gives a maintenance number of about 2,000 calories. When in doubt, choose the lower level. Most people overestimate how active they are, and if your factor already counts your workouts, the exercise calories guide explains why you shouldn’t add them again.

Step 3: Pick a Pace

A pound of body fat is often said to hold about 3,500 calories, so cutting 500 calories a day works out to roughly a pound a week at first. The 2013 obesity guidelines from the American Heart Association and partner groups take a similar line. They recommend a daily deficit of 500 to 750 calories for most adults with overweight or obesity, according to the published guideline.

A smaller cut is also reasonable, especially if you have less to lose. A practical limit is to lose no more than about 1% of your body weight a week, because faster loss usually means more hunger and more lost muscle.

The example woman chooses 500 calories, so her target is about 1,500 calories a day. At 170 pounds, a pound a week is also well under 1% of her weight.

Step 4: Check the Floor

The last step is a safety check. The same guidelines describe typical weight-loss intakes of 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men. They also say diets under 800 calories belong only in medical settings with close supervision.

So if your result falls below 1,200 calories as a woman or 1,500 as a man, use the floor instead and accept slower loss. Smaller, older and less active people hit the floor most often. In the third example below, the floor means losing about half a pound a week instead of a full pound.

Why the Number Changes Over Time

The 3,500-calorie rule is a useful starting point, but it overpromises over months. Researchers compared its predictions with closely supervised weight-loss studies and found that it consistently overestimated how much weight people actually lost, according to a 2013 analysis.

The main reason is that your body burns less as it gets smaller. Each pound lost lowers your resting burn a little, so a deficit of 500 calories on day one shrinks over time. Weight also responds slowly to any change in eating, with modeling work putting the half time at about a year. On top of that, the body defends its fat stores through hormonal signals that raise appetite, as described in a review of adaptive thermogenesis.

In practice, recalculate your target after every 10 to 15 pounds lost. The weight loss plateau guide shows how much the number typically drops.

Test Your Number Against the Scale

A formula is only an estimate, so treat your first target as a hypothesis. Eat at that number for two to four weeks, log honestly and compare weekly average weights rather than single weigh-ins. Daily swings from water and food can hide real progress, as the daily fluctuation guide explains.

Logging accuracy matters as much as the target. In one well-known study, people who believed they couldn’t lose weight underreported their food by 47% on average, according to the 1992 NEJM study. Weighing foods and counting cooking oils closes most of that gap, and the raw vs cooked guide covers the most common logging mistake.

1. Losing about as planned? Keep the number and recheck it after the next 10 pounds.
2. Losing faster than 1% a week? Add 100 to 200 calories so the pace stays sustainable.
3. Not losing after four weeks? Check your logging first, then lower the target by 100 to 200 calories, staying above the floor.

Common Questions

The Bottom Line

Your calorie target comes from four steps. Estimate your resting burn, multiply by an honest activity factor, subtract 250 to 750 calories and keep the result above 1,200 for women or 1,500 for men. For most people, that lands between 1,200 and 1,800 calories a day.

The number is an estimate, so test it for two to four weeks against your weekly average weight and adjust by 100 to 200 calories when needed. Recalculate as you lose, log carefully and talk with a doctor if you have a medical condition. A good target is simply one you can follow consistently.