How to Calculate a Calorie Deficit (Step by Step)

Every weight loss plan, from keto to intermittent fasting, works the same way underneath: you eat a little less energy than your body uses. Knowing how to calculate a calorie deficit takes the guesswork out of that process. Instead of slashing food and hoping for the best, you get a realistic daily target built around your body and lifestyle.

This guide walks through the formula, a full worked example, how much protein to aim for, and what to do when progress stalls.

What Is a Calorie Deficit?

A calorie deficit means taking in fewer calories than you burn. When that happens consistently, your body makes up the difference with stored energy, mostly fat. The bigger the gap, the faster you lose weight, but also the hungrier and more tired you're likely to feel.

Your daily energy use comes from three main sources: the energy needed to keep you alive at rest, the energy used to digest food, and the energy from all your movement, from workouts to walking around the house. To calculate a deficit, you estimate that total and then eat a little below it.

Step 1: Estimate Your BMR

Basal metabolic rate (BMR) is the number of calories your body burns at complete rest to keep your heart beating, lungs breathing and organs working. It's usually the largest part of your daily burn.

The Mifflin-St Jeor equation is one of the most widely used and reliable ways to estimate it. It uses weight in kilograms, height in centimeters and age in years:

• Men: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5
• Women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161

Step 2: Multiply by Your Activity Level to Find TDEE

Total daily energy expenditure (TDEE) is your BMR plus everything else you do in a day. To estimate it, multiply your BMR by the activity factor that best matches your typical week.

Be honest here. Most people overestimate how active they are. If you're torn between two levels, pick the lower one.

Step 3: Choose a Safe Calorie Deficit

Once you have your TDEE, subtract a deficit to get your daily calorie target. For most people, roughly 300 to 500 calories a day is the sweet spot. It's big enough to see progress and small enough to keep up without feeling miserable.

A good way to check your pace is to aim for losing about 0.5 to 1 percent of your body weight per week. For a 200-pound person, that's about 1 to 2 pounds weekly. Smaller people, and people who are already fairly lean, should stay toward the lower end.

How to Calculate a Calorie Deficit: A Worked Example

Let's put it together for a 35-year-old woman who is 5 feet 5 inches tall (165 cm), weighs 165 pounds (75 kg), and walks or does light workouts a few days a week.

1. Calculate BMR. (10 × 75) + (6.25 × 165) − (5 × 35) − 161 = 750 + 1,031 − 175 − 161 = about 1,445 calories.
2. Find TDEE. She's lightly active, so 1,445 × 1.375 = about 1,990 calories a day.
3. Subtract a deficit. A 400-calorie deficit gives a target of about 1,590 calories a day. Rounding to 1,600 is fine.
4. Check the pace. One percent of 165 pounds is about 1.6 pounds. Her deficit should produce roughly 0.75 to 1 pound a week, comfortably within the safe range.

Don't want to do the math by hand? The calorie calculator at the end of this article does it for you.

Don't Forget Protein

When you're eating less, you want the weight you lose to come from fat, not muscle. Two things help most: eating enough protein and doing some strength training.

Many experts suggest roughly 1.2 to 2.0 grams of protein per kilogram of body weight per day while losing weight, with around 1.6 g/kg being a solid target for active people. For our example, that's about 120 grams a day, or 30 to 40 grams per meal. Use our protein calculator or read how much protein you need for more detail.

Protein also keeps you fuller, which makes the deficit easier to stick with. Build meals around eggs, Greek yogurt, fish, chicken, tofu or beans. Our list of healthy breakfast foods for weight loss has easy ideas, and the beginner strength training guide gets you started with lifting.

Track, Adjust and Handle Plateaus

Every formula is an estimate. Your real TDEE could be a few hundred calories higher or lower. That's why tracking matters more than the starting number.

How to track

• Weigh yourself a few mornings a week under the same conditions, and compare weekly averages.
• Log your food for at least two weeks to see whether you're really hitting your target.
• Take waist measurements or photos every few weeks, since the scale doesn't tell the whole story.

When progress stalls

As you lose weight, your body needs fewer calories, so a deficit that worked at the start gets smaller over time. If your weekly average hasn't moved in two to three weeks:

1. Check your accuracy. Oils, sauces, drinks and weekend meals are common hidden sources of calories.
2. Move more. Adding daily steps is often easier than eating less. See our walking for weight loss plan.
3. Recalculate. Plug your new weight into the formula and reduce your target by 100 to 200 calories if needed.
4. Take a break. A week or two at maintenance can help if you feel run down after months of dieting.

Knowing how to calculate a calorie deficit is a starting point, not a life sentence of counting. Once you learn what your portions look like, many people move to a looser approach while keeping an eye on their weight trend. For more habits that make the process easier, read our 29 essential ways to lose weight naturally.

If you have a medical condition, are pregnant or breastfeeding, or have a history of disordered eating, work with your doctor or a registered dietitian rather than setting a deficit on your own.