How Many Calories Should I Eat?

The question "how many calories should I eat?" looks simple, but the honest answer depends on your age, sex, height, weight, activity level, and goal. The good news is that researchers have built a reliable, science-based framework for estimating daily calorie needs: you calculate your basal metabolic rate (BMR), convert it into total daily energy expenditure (TDEE), then adjust up or down depending on whether you want to lose, maintain, or gain weight. This guide walks through each step so you can land on a number that actually works for your body.

Understanding BMR: the energy your body needs at rest

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest, just to keep you alive. That covers breathing, circulation, cell production, nutrient processing, and body temperature regulation. BMR typically accounts for 60–75% of your total daily energy expenditure, which is why it matters so much for setting a calorie target.

The most widely validated formula for estimating BMR is the Mifflin-St Jeor equation, published in 1990 and adopted by most modern nutrition tools. The equations are:

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

As an example, a 30-year-old woman who is 165 cm tall and weighs 70 kg would have a BMR of roughly 1,415 calories. That is the floor — the energy her body demands before she takes a single step. Your calorie calculator handles this math automatically so you can skip the arithmetic.

From BMR to TDEE: factoring in activity

BMR tells you what you burn lying still, but nobody lives motionless. Total daily energy expenditure (TDEE) multiplies your BMR by an activity factor to reflect how much you move throughout the day. The five standard activity multipliers are:

Activity level	Multiplier	Description
Sedentary	1.2	Little or no exercise, desk job
Lightly active	1.375	Light exercise 1–3 days/week
Moderately active	1.55	Moderate exercise 3–5 days/week
Very active	1.725	Hard exercise 6–7 days/week
Extra active	1.9	Very hard exercise or physical job

So our 70 kg, 165 cm, 30-year-old woman with a BMR of about 1,415 would have a TDEE of roughly 1,945 calories if sedentary, 2,390 if moderately active, and 2,662 if very active. The difference between sedentary and very active is over 700 calories a day — which is why adding movement is often a more sustainable lever than cutting food.

Be honest with yourself when picking a multiplier. Most people overestimate how active they are. If you train hard for an hour but sit the other 23, "moderately active" (1.55) is usually closer than "very active."

Calculating a calorie deficit for weight loss

Once you have your TDEE, weight loss math is straightforward in principle: eat less than you burn. One pound of body fat contains roughly 3,500 calories, so a daily deficit of 500 calories produces about one pound of loss per week, and a 1,000-calorie daily deficit produces about two pounds per week.

Using our example: if her TDEE is 2,390 and she wants to lose one pound per week, her target intake is 2,390 − 500 = 1,890 calories per day. You can plug your own numbers into a calorie calculator to get a personalized target without doing the manual math.

A few practical principles keep the deficit approach sustainable:

• Start moderate. A 15–25% deficit below TDEE tends to preserve muscle and energy better than an aggressive cut.
• Track for two to three weeks, then adjust. Real-world intake and expenditure vary, so compare your actual weight trend to the prediction and recalibrate.
• Recalculate as you lose. A smaller body burns fewer calories, so your TDEE drops. Re-run the numbers every 10–15 pounds.
• Prioritize protein. Higher protein intakes protect lean mass and increase satiety, making the deficit feel easier.

If you want a guided, psychology-informed approach rather than going it alone, Noom pairs calorie targets with behavioral coaching to help you build habits that stick.

Minimum safe calorie intakes

More deficit is not always better. Very low calorie diets can trigger metabolic adaptation (where your BMR slows to conserve energy), muscle loss, hormonal disruption, and nutrient deficiencies. The commonly cited safety floors are:

• Women: no less than 1,200 calories per day
• Men: no less than 1,500 calories per day

These are minimums for the general population, not targets. If your calculated deficit would drop you below these floors, the safer move is to increase activity rather than to cut food further. Anyone considering a medically supervised very-low-calorie diet should do so only under professional guidance.

Macronutrient breakdown: what your calories are made of

A calorie target tells you how much to eat; your macronutrient split tells you what those calories should be made of. The three macronutrients — protein, carbohydrates, and fat — each serve different functions, and the ratio you choose affects body composition, satiety, and performance.

Macro	Calories per gram	Key roles
Protein	4	Muscle repair, satiety, immune function
Carbohydrate	4	Primary fuel, especially for exercise
Fat	9	Hormone production, nutrient absorption

A balanced starting point for general health is roughly 30% protein, 40% carbs, 30% fat. For a 1,800-calorie intake, that works out to about 135 g protein, 180 g carbs, and 60 g fat. Athletes or people in a building phase often tilt toward more carbs and protein; people prioritizing satiety in a cut may push protein higher.

To track all of this accurately, a logging app like MyFitnessPal makes the process nearly frictionless — scan a barcode, see the macros, and adjust in real time.

The role of activity and training

Diet drives the calorie equation, but activity reshapes the variables in your favor. Resistance training in particular is worth its weight: it preserves (and can build) lean muscle mass during a deficit, which keeps your BMR higher and your body composition healthier. Cardio is useful for increasing energy expenditure and cardiovascular health, but it does not protect muscle the way lifting does.

A practical weekly structure for most people:

• 2–4 resistance training sessions, focusing on compound movements
• 2–3 cardio sessions (walking, cycling, or similar)
• 7,000–10,000 steps of daily incidental movement
• 1–2 full rest or active recovery days

Structured programs take the guesswork out of training. Beachbody on Demand offers streaming workouts that pair well with a calorie target, letting you rotate between strength, cardio, and mobility without planning each session yourself.

Why your calorie needs change over time

A calorie target is a snapshot, not a permanent setting. Several factors shift your needs:

• Weight change: as you lose (or gain) weight, your BMR moves with it. Re-calculate periodically.
• Age: BMR naturally declines with age, largely due to muscle loss. Resistance training offsets this.
• Muscle mass: more lean tissue means a higher BMR, even at rest.
• Metabolic adaptation: sustained deficits can lower BMR more than the equations predict, which is why diet breaks and refeeds are useful for long diets.
• Health and hormones: thyroid function, sleep, stress, and certain medications all influence energy expenditure.

Putting it all together

Here is the full workflow for landing on your calorie target:

• Calculate your BMR using the Mifflin-St Jeor equation.
• Multiply by the activity factor that honestly matches your lifestyle to get TDEE.
• Subtract 500 calories for ~1 lb/week loss, or 1,000 for ~2 lbs/week. Add calories above TDEE to gain.
• Check against the 1,200/1,500 minimums. If you are at or below them, add activity instead.
• Set your macros — start around 30/40/30 and adjust based on hunger, performance, and results.
• Track intake and weight for two to three weeks, then adjust the target based on the trend.

The bottom line

"How many calories should I eat?" comes down to a reliable three-step process: find your BMR, scale it to TDEE with an honest activity factor, and adjust by 500 calories per pound of desired weekly weight change. Stay above the 1,200/1,500 safety floors, keep protein high, include resistance training, and re-run the numbers as your body changes. Use a calorie calculator to handle the math, and lean on tools like Noom, MyFitnessPal, or Beachbody on Demand when you want coaching, tracking, or training support. The number you land on is a starting point — the real results come from consistency and honest recalibration.