You open a food app, it asks for a calorie goal, and you freeze. Is it 1,500? 1,800? 2,000? If you have ever typed "how many calories should I eat to lose weight" into a search bar at 11 p.m., you are in good company. Here's the good news: you don't need to guess. Your number comes from a short, simple bit of math, and you can do it in about five minutes.
Let me walk you through it, step by step. Or skip the math and use our calorie calculator, which does the same steps for you.
Why your calorie number is personal
Your body burns energy all day, even when you sleep. How much it burns depends on your size, age, sex, and how much you move. That is why a friend's number may not work for you.
To lose weight, you eat a bit less than your body burns. That gap is called a calorie deficit. The trick is making the gap big enough to see progress, but small enough that you can live with it.
How many calories should I eat to lose weight? The 3-step method
This is simpler than it sounds. There are three steps:
- Find your BMR (the calories you burn at rest).
- Multiply by your activity level to get your maintenance calories.
- Take off about 20% for weight loss.
Step 1: Find your BMR
BMR stands for basal metabolic rate. It is the energy your body uses just to keep you alive: breathing, pumping blood, keeping warm.
Most calculators, including ours, use the Mifflin-St Jeor equation. Researchers built it in 1990 from 498 healthy adults whose resting burn was measured in a lab. A 2005 review for the American Dietetic Association found it was the most likely of the common equations to land within 10% of a person's measured resting burn.
Here is the formula. Use weight in kilograms, height in centimeters, and age in years.
- Women: (10 × weight) + (6.25 × height) - (5 × age) - 161
- Men: (10 × weight) + (6.25 × height) - (5 × age) + 5
To convert: 1 lb = 0.4536 kg, and 1 inch = 2.54 cm.
Step 2: Multiply by your activity level
Next, you multiply your BMR by an activity factor. This gives your maintenance calories, also called TDEE (total daily energy expenditure). It is the amount that keeps your weight steady.
| Activity level | What it looks like | Multiply BMR by |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1 to 3 days a week | 1.375 |
| Moderately active | Exercise 3 to 5 days a week | 1.55 |
| Very active | Hard exercise 6 to 7 days a week | 1.725 |
| Extremely active | Hard daily training or a physical job | 1.9 |
Be honest here. If you are stuck between two levels, pick the lower one. You can always adjust later. Our TDEE calculator shows your number at every level side by side.
Step 3: Take off about 20%
For weight loss, our calculators take 20% off your maintenance calories. So you multiply maintenance by 0.8. That is it. You have your starting number.
Worked example for a woman
When I ran the numbers for a 40-year-old woman who is 5 ft 5 in (165.1 cm), weighs 170 lb (77.1 kg), and is lightly active, using the same formula our calculator uses, here is what came out:
- 10 × 77.1 = 771
- 6.25 × 165.1 = 1,031.9
- 5 × 40 = 200
- BMR = 771 + 1,031.9 - 200 - 161 = about 1,440 calories
- Maintenance = 1,441.9 × 1.375 = about 1,980 calories
- Weight-loss target = 1,982.6 × 0.8 = about 1,590 calories a day
So her answer is roughly 1,590 calories a day. That leaves plenty of room for real, filling meals.
Worked example for a man
Now a 45-year-old man who is 5 ft 10 in (177.8 cm), weighs 200 lb (90.7 kg), and works out 3 to 5 days a week (moderately active):
- 10 × 90.7 = 907
- 6.25 × 177.8 = 1,111.3
- 5 × 45 = 225
- BMR = 907 + 1,111.3 - 225 + 5 = about 1,800 calories
- Maintenance = 1,798.3 × 1.55 = about 2,790 calories
- Weight-loss target = 2,787.4 × 0.8 = about 2,230 calories a day
Notice how much higher his number is. Cutting him to 1,500 would be a far bigger gap than the 20% plan calls for.
The safety floor: when 20% is too much
This is where it gets interesting. For smaller or older people, a 20% cut can drop very low.
Take a 60-year-old woman who is 5 ft 0 in (152.4 cm), weighs 120 lb (54.4 kg), and is sedentary. Her BMR is about 1,040 calories. Her maintenance is about 1,240. A 20% cut would be about 990 calories.
That is why our calculators never suggest less than 1,200 calories a day for women or 1,500 for men. In her case, the calculator shows 1,200 and flags that the floor was used. That floor is a safety line, not a target to aim for.
If your number lands near the floor, a slower pace or more daily movement may suit you better. And if you are pregnant, have diabetes or kidney disease, take medicines that affect appetite or blood sugar, or have a history of an eating disorder, talk to your doctor or a registered dietitian before cutting calories.
How fast will you lose weight?
Here's the thing: the old rule says 3,500 calories equals 1 pound (0.45 kg) of fat. It is easy math, but it is not the full story.
A 2011 study in The Lancet by Kevin Hall and colleagues at the National Institutes of Health showed that your body weight responds slowly to a change in eating. Their model found half times of about 1 year. In plain words, as you lose weight, you burn a little less, so weight loss slows over time. The simple 3,500 rule tends to overestimate how much you will lose in the long run.
If you want a more realistic forecast, the NIH Body Weight Planner is built on Hall's model.
For pace, the CDC says people who lose weight at a gradual, steady rate of about 1 to 2 pounds (0.5 to 0.9 kg) a week are more likely to keep it off. The CDC also gives a helpful example. For a person who weighs 200 lb (91 kg), a 5% loss is 10 lb (4.5 kg). That change could lower the risk for some chronic diseases such as heart disease, prediabetes, and type 2 diabetes.
That is a win you can feel good about, even if the scale never hits some "perfect" number.
Make your calories work harder with protein
When you eat less, you want to keep your muscle. Protein helps. The International Society of Sports Nutrition says 1.4 to 2.0 g of protein per kg of body weight a day is enough for most people who exercise. For a 170 lb (77 kg) person, that is about 108 to 154 g a day.
That sounds like a lot. But a few smart swaps make it easy. Our protein calculator gives you a daily target for weight loss.
Eating out on a calorie target
You don't have to cook every meal. A few chain orders fit a calorie target well:
| Chain | Order | Calories | Protein |
|---|---|---|---|
| Chick-fil-A | 8 ct Grilled Nuggets | 130 | 25 g |
| Chipotle | High Protein - Low Calorie Bowl | 460 | 35 g |
| Subway | Subway Club Protein Bowl | 410 | 44 g |
See more in our list of top protein picks at fast food chains.
What this means for you
Based on what I've seen in the research, the formula is a great starting point, not a final answer. The Frankenfield review found Mifflin-St Jeor was the most reliable common equation, but the authors also warned it can be off for some people, and that older adults and some ethnic groups were underrepresented in the research.
So treat your number like a first draft:
- Eat at your target for 2 to 3 weeks.
- Weigh yourself a few mornings a week and look at the weekly average, not single days.
- If your average hasn't moved, lower your target by about 100 to 200 calories (never below the floor), or add more walking.
- If you are losing faster than 2 lb (0.9 kg) a week and feel worn out, eat a bit more.
Once you do this once, it becomes second nature. Want to understand the gap itself in more depth? Read our guide on how to calculate a calorie deficit.
My take
I like the 20% approach because it scales with you. A tall, active man and a petite, sedentary woman get very different numbers, which is exactly how it should be. A fixed "eat 1,200 calories" rule ignores all of that.
The part people skip is step 4, the adjusting. That is where real progress happens.
The bottom line
So, how many calories should you eat to lose weight? Find your BMR, multiply by your activity level, and take off about 20%. Your friend's number doesn't matter. Your own number is the one that counts. Plug your details into our calorie calculator, give it a few weeks, and adjust. You've got this.