April 19, 2026 12 min read Michal

How Many Calories Should I Eat Per Day? The Complete Guide

“How many calories should I eat?” has no single answer. It depends on your age, sex, height, weight, activity level, and goal — but you don't need a degree in nutrition to figure it out.

This guide walks you through the calculation in four steps. By the end, you'll have your personalized daily calorie target for weight loss, maintenance, or muscle building.

The Short Answer

Most adults need 1,600–3,000 calories per day to maintain their weight: 1,600–2,400 for women and 2,000–3,000 for men, according to the estimates of the Dietary Guidelines for Americans 2020–2025 (Appendix 2). The exact number depends on your age, sex, height, weight, and how active you are.

The ranges for adults by activity level:

Gender	Sedentary	Moderately Active	Active
Women (19+)	1,600–2,000 kcal	1,800–2,200 kcal	2,000–2,400 kcal
Men (19+)	2,000–2,600 kcal	2,200–2,800 kcal	2,400–3,000 kcal

But these are estimates for a reference woman (163 cm, 57 kg) and a reference man (178 cm, 70 kg). Sedentary means only the activity of daily living; moderately active adds the equivalent of walking 2.4–4.8 km a day at 4.8–6.4 km/h; active, more than 4.8 km. The 2025–2030 edition of the guidelines has no such table — it says only that the calories you need depend on your age, sex, height, weight, and level of physical activity. To find your number, calculate it in four steps: BMR → TDEE → TEF → Goal Adjustment.

Step 1: Calculate Your BMR (Basal Metabolic Rate)

Your BMR is the number of calories your body burns at complete rest — just keeping your organs running, maintaining body temperature, and breathing. For a sedentary or lightly active person, BMR is about 60–70% of the day’s calorie burn (FAO/WHO/UNU 2004).

The formula AI Food Coach uses by default is Mifflin-St Jeor. Mifflin and St Jeor derived it in 1990 from 498 healthy adults aged 19–78 whose resting energy was measured by indirect calorimetry; in the same people, the 1919 Harris-Benedict equations overestimated it by 5% (Mifflin 1990). It uses four variables: weight, height, age, and sex:

Men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
Women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161

Example: A 30-year-old woman, 65 kg, 165 cm:

BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161
BMR = 650 + 1,031 − 150 − 161 = 1,370 kcal

This means her body burns about 1,370 kcal per day just by existing — before any movement or exercise.

What about Katch-McArdle?

If you know your body fat percentage, the Katch-McArdle formula uses lean body mass instead of total weight: BMR = 370 + (21.6 × lean_mass_kg) (Cunningham 1991). Resting energy depends mostly on lean mass, which makes it more accurate for people with higher or lower than average body fat. AI Food Coach switches to it automatically when you set your body fat. Read more about how TDEE formulas work.

Use our free TDEE Calculator → to get your BMR and TDEE instantly without manual math.

Step 2: Multiply by Activity Level (= Your TDEE)

BMR is only your resting calorie burn. To get your TDEE (Total Daily Energy Expenditure) — the total calories you burn including movement — multiply your BMR by an activity factor. These are the multipliers commonly used with BMR equations — AI Food Coach uses the same ones:

Activity Level	Multiplier	Description
Sedentary	1.2	Desk job, little exercise
Light	1.375	1–2 workouts a week
Moderate	1.55	3–5 workouts a week
Active	1.725	6–7 workouts a week
Very Active	1.9	Athlete, physical job

Example continued: Our 30-year-old woman works out 3–4 times a week (Moderate):

TDEE = 1,370 × 1.55 = 2,124 kcal

This is her base TDEE — BMR multiplied by activity level. AI Food Coach adds the energy her body spends digesting food (TEF) on top of it, as the next step explains.

With a smartwatch, the number follows your day

A multiplier gives the same number every day — but real activity varies. If you wear an Apple Watch, AI Food Coach uses the resting and active energy the watch records in Apple Health instead of the formula and the multiplier. These are estimates too: Apple says the watch uses your height, weight, sex and age, among other things, and in a study of seven wrist devices none estimated energy expenditure within 20% — Apple Watch came closest (Shcherbina 2017). The app reads yesterday’s resting energy, ignores a value below 70% of your formula BMR, and counts it only together with active energy. On Android, the app uses the calories your watch writes to Health Connect.

Step 3: Account for the Thermic Effect of Food (TEF)

Your body burns calories digesting food — this is called the Thermic Effect of Food (TEF), about 10% of the day’s energy on a mixed diet. Different macronutrients cost different amounts of energy to process (the measured ranges from Westerterp 2004; AI Food Coach uses the values of Hall 2010):

Protein: 20–30% of its calories are burned during digestion (the app uses 25%)
Carbohydrates: 5–10% (7.5%)
Fat: 0–3% (2.5%)

Example continued: Assuming our woman eats a balanced diet (30% protein, 40% carbs, 30% fat) at her base TDEE of 2,124 kcal:

TEF = (2,124 × 0.30 × 0.25) + (2,124 × 0.40 × 0.075) + (2,124 × 0.30 × 0.025)
TEF = 159 + 64 + 16 = ~239 kcal/day

Her complete TDEE including TEF: 2,124 + 239 = 2,363 kcal/day. That’s 11% more than the base calculation — a meaningful difference for setting accurate calorie targets.

With 40% of the calories from protein (and 30% each from carbs and fat), TEF comes to about 13% of intake (~280 kcal/day at 2,124 kcal). On a high-fat, low-protein diet (20% protein, 5% carbs, 75% fat), it drops to about 7% (~150 kcal/day). The macro composition of your diet changes how many calories digestion takes.

Why add TEF on top?

The resting and active energy from your watch, Apple Health or Health Connect do not include TEF, so the app adds it. Without Health data it adds TEF to BMR × activity multiplier as well: the usual multipliers are lower than the physical activity levels measured in the FAO/WHO/UNU energy report (total ÷ basal energy expenditure — 1.40–1.69 for a sedentary or lightly active lifestyle), and Sedentary 1.2 plus TEF comes to about 1.3. AI Food Coach calculates TEF from the macros you actually log. Try our TEF Calculator to see your number.

Step 4: Adjust for Your Goal

Your complete TDEE (including TEF from Step 3) tells you about how many calories you burn. What you eat relative to that number determines whether you lose, maintain, or gain weight.

Weight Loss (Calorie Deficit)

To lose weight, eat fewer calories than your TDEE. The size of the deficit determines how fast you lose:

The commonly used estimate is 7,700 kcal per kilogram of body fat. So:

275 kcal/day deficit → ~0.25 kg lost per week (gentle)
550 kcal/day deficit → ~0.5 kg lost per week (moderate)
825 kcal/day deficit → ~0.75 kg lost per week (aggressive)
1,100 kcal/day deficit → ~1 kg lost per week (the app’s maximum)

AI Food Coach allows at most 1 kg a week. The CDC notes that people who lose weight at a gradual, steady pace — about 1–2 pounds (0.5–1 kg) a week — are more likely to keep the weight off.

Example continued: Our woman wants to lose 0.5 kg per week — a deficit of 550 kcal a day. AI Food Coach subtracts it from her base TDEE and adds the TEF of what she eats:
Target = 2,124 − 550 + TEF of her food = 1,574 + TEF
If she eats about 1,770 kcal in the same 30/40/30 split, TEF comes to about 200 kcal, so her target ends the day at about 1,770 kcal.

AI Food Coach never sets a target below 1,200 kcal for women or 1,500 kcal for men — the lower end of the diets the AHA/ACC/TOS 2013 obesity guideline prescribes for weight loss (1,200–1,500 kcal a day for women, 1,500–1,800 for men, adjusted for body weight). Very-low-calorie diets, under 800 kcal a day, belong only in a medical setting with monitoring, the same guideline says.

Your weight loss target: your TDEE minus the deficit for the pace you choose — the same guideline names a deficit of 500 or 750 kcal a day as one way to lose weight. Use our TDEE Calculator to find your number.

Weight Maintenance

Eat at your complete TDEE (including TEF). In our example, that’s 2,363 kcal — not the 2,124 base calculation. This sounds simple, but a formula you ran once is only an estimate of your actual TDEE.

Your TDEE changes as your weight, activity, and body composition change. A person who loses 10 kg gets a lower BMR from Mifflin-St Jeor, which uses body weight, so the amount that kept their old weight is now more than they burn.

The solution is to track your weight alongside your calories. In AI Food Coach, the Stay Healthy goal does it for you: it compares your 7-day average weight with the weight you hold. Within ±0.5 kg nothing changes; further off, with Dynamic Targets on, it adds a small deficit or surplus — at most 0.25 kg a week — until you are back.

Muscle Building (Calorie Surplus)

To build muscle, eat more than your TDEE. How large a surplus gains the most muscle is not known (Slater 2019); a review for natural bodybuilders recommends about 10–20% above maintenance and a gain of about 0.25–0.5% of body weight a week for beginners and intermediates, less for advanced lifters (Iraki 2019) — 0.2–0.4 kg a week at 80 kg. AI Food Coach allows at most 0.5 kg a week (about 550 kcal a day).

Protein matters here too. In a meta-analysis of 49 studies, muscle gains from resistance training plateaued at about 1.6 g of protein per kg of body weight a day, with a confidence interval up to 2.2 g/kg (Morton 2018). For an 80 kg man, that is 128–176 g of protein per day.

Good high-protein sources include chicken breast (30.5 g protein per 100 g, 151 kcal, grilled) and eggs (12.6 g protein per 100 g, 143 kcal).

How Many Calories Should a Woman Eat?

The following table shows estimated daily calorie needs for women at three activity levels, from the Dietary Guidelines for Americans 2020–2025 (Appendix 2, Table A2-2). These are maintenance calories — for weight loss, subtract the deficit for your pace (550 kcal a day for 0.5 kg a week).

Age	Sedentary	Moderately Active	Active
19–25	2,000 kcal	2,200 kcal	2,400 kcal
26–30	1,800 kcal	2,000 kcal	2,400 kcal
31–50	1,800 kcal	2,000 kcal	2,200 kcal
51–60	1,600 kcal	1,800 kcal	2,200 kcal
61+	1,600 kcal	1,800 kcal	2,000 kcal

These numbers are for a reference woman 163 cm tall who weighs 57 kg. Your individual needs may be higher or lower depending on your body size and composition. A tall, muscular woman will need more than a petite woman of the same age — which is why calculating your personal BMR and TDEE gives a more personal answer than any table.

You can also check your BMI as a starting reference point, but keep in mind that BMI does not account for muscle mass or body composition.

How Many Calories Should a Man Eat?

The same table gives the estimates for men (reference man: 178 cm, 70 kg):

Age	Sedentary	Moderately Active	Active
19–20	2,600 kcal	2,800 kcal	3,000 kcal
21–25	2,400 kcal	2,800 kcal	3,000 kcal
26–35	2,400 kcal	2,600 kcal	3,000 kcal
36–40	2,400 kcal	2,600 kcal	2,800 kcal
41–45	2,200 kcal	2,600 kcal	2,800 kcal
46–55	2,200 kcal	2,400 kcal	2,800 kcal
56–60	2,200 kcal	2,400 kcal	2,600 kcal
61–65	2,000 kcal	2,400 kcal	2,600 kcal
66–75	2,000 kcal	2,200 kcal	2,600 kcal
76+	2,000 kcal	2,200 kcal	2,400 kcal

Men generally need more calories than women, and calorie needs decrease with age as the basal metabolic rate falls — in these tables the gap between men and women shrinks from 600 to 400 kcal. When you pick your activity level, count your workouts: a desk job with three workouts a week is Moderate in AI Food Coach (3–5 workouts a week), not Active. With Apple Health on, the app sets the level from the workouts it records.

How to Track Your Calories (Without Going Crazy)

Knowing your calorie target is only useful if you can track what you eat. The good news: modern tools make this much easier than manually looking up every food in a database.

1. Photo AI Recognition

Take a photo of your meal and let AI estimate the calories and macros. For better accuracy, place your food on a kitchen scale so the AI can read the weight from the display.

2. Manual Entry and Search

Search for foods by name or enter nutrition values manually. For common foods, the calorie count is well established — for example, cooked white rice is about 130 kcal per 100 g, and a large egg (50 g) is about 72 kcal.

3. Barcode Scanning

Scan the barcode on packaged foods to load the label’s values from Open Food Facts, a product database its users fill in from the packages. Check them against the label — then you log what the manufacturer printed.

The best tracking method is the one you will actually use. A photo is quick, a barcode brings the label’s values for packaged foods, and manual entry gives you full control — you can mix all three.

AI Food Coach combines all three methods in one app — snap a photo, scan a barcode, or type in your food. It calculates your TDEE from your profile and, with Apple Health or Health Connect, from what your watch records, and your calorie target grows with the TEF of what you eat.

Common Mistakes When Counting Calories

1. Eating Too Few Calories

Cutting calories hard can look like a shortcut. For weight loss, the AHA/ACC/TOS 2013 guideline prescribes 1,200–1,500 kcal a day for women and 1,500–1,800 for men, and keeps very-low-calorie diets (under 800 kcal a day) for a medical setting with monitoring, because of the rapid weight loss and the potential for health complications. AI Food Coach never sets a target below 1,200 kcal for women or 1,500 kcal for men.

2. Not Counting Liquid Calories

Juice, soda, alcohol, milk in coffee, smoothies — these add up quickly. A medium latte (355 ml) has about 153 kcal, a glass of orange juice (248 g) about 112 kcal, and two glasses of red wine (150 ml each) about 255 kcal. Log them like food.

3. Ignoring the Thermic Effect of Food (TEF)

Your body burns calories digesting food. Protein has the highest thermic effect — the app counts 25% of its calories, carbohydrates 7.5% and fat 2.5% (Hall 2010). In the example above that is about 240 kcal a day — AI Food Coach adds it automatically from your logged meals.

The more of your calories come from protein, the more digestion takes. Try our TEF Calculator to see how much your diet composition affects your daily burn.

See our full methodology and scientific sources →

Frequently Asked Questions

How many calories should I eat to lose weight?

To lose weight, eat fewer calories than your body burns (your TDEE). A deficit of 550 kcal a day comes to about 0.5 kg a week by the commonly used estimate of 7,700 kcal per kilogram of body fat. For weight loss, the AHA/ACC/TOS 2013 guideline prescribes 1,200–1,500 kcal a day for women and 1,500–1,800 kcal for men, adjusted for body weight. AI Food Coach never sets a target below 1,200 kcal for women or 1,500 kcal for men.

How many calories do I need to lose 1 kg per week?

By the commonly used estimate of 7,700 kcal per kilogram of body fat, losing 1 kg a week takes a daily deficit of about 1,100 kcal (7,700 / 7). That is the most AI Food Coach allows; the CDC notes that people who lose about 1–2 pounds (0.5–1 kg) a week are more likely to keep the weight off. With a TDEE of 2,500 kcal, the target would be about 1,400 kcal plus the TEF of what you eat.

Is 1,200 calories a day enough?

1,200 kcal a day is the lower end of what the AHA/ACC/TOS 2013 guideline prescribes for weight loss in women (1,200–1,500 kcal); for men the range starts at 1,500 kcal. Diets under 800 kcal a day belong only in a medical setting with monitoring. AI Food Coach never sets a target below 1,200 kcal for women or 1,500 kcal for men — if the calculation comes out lower, the target is set to that minimum.

How many calories does walking 10,000 steps burn?

It depends on your weight and pace. In adults aged 21–40, walking at about 100 steps a minute was moderate intensity, about 3 METs, and about 130 steps a minute vigorous, about 6 METs (Tudor-Locke 2019). One MET is about 1 kcal per kg of body weight per hour, the body at rest (Herrmann 2024). So for a 75 kg person, 10,000 steps burn about 250 kcal above rest at 100 steps a minute (100 minutes) and about 480 kcal at 130 steps a minute (77 minutes). Apple Watch estimates it from your heart rate and movement — an estimate too (Shcherbina 2017).

Should I eat back exercise calories?

It depends on how your calorie target is calculated. If your target already includes an activity multiplier (like Moderate), your exercise is already in it — eating it back would count it twice. With Apple Health on, AI Food Coach does not use the multiplier: it adds the active energy your watch or phone records to your target as it comes in. Those numbers are estimates (Shcherbina 2017), so with Dynamic Deficit on (Dynamic Surplus when you build muscle) the app also re-plans your pace from your 7-day average weight.

How accurate are calorie calculators?

A formula estimates the energy of an average person of your weight, height, age and sex — your own can be higher or lower, and watches estimate too (Shcherbina 2017). The other side is food: portion estimation, forgotten snacks, and nutrition labels. A food scale, barcodes, and photos of food on the scale help. The most reliable check is your weight over weeks: with Dynamic Deficit on (Dynamic Surplus when you build muscle), AI Food Coach re-plans your pace from your 7-day average weight.

Sources

U.S. Department of Agriculture and U.S. Department of Health and Human Services. (2020). Dietary Guidelines for Americans, 2020–2025, Appendix 2, Table A2-2: Estimated Calorie Needs per Day, by Age, Sex, and Physical Activity Level. DietaryGuidelines.gov
U.S. Department of Health and Human Services and U.S. Department of Agriculture. (2026). Dietary Guidelines for Americans, 2025–2030. RealFood.gov
FAO/WHO/UNU. (2004). Human energy requirements: report of a joint FAO/WHO/UNU Expert Consultation. FAO Food and Nutrition Technical Report Series 1. FAO
Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 51(2):241-247. AJCN
Cunningham JJ. (1991). Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. American Journal of Clinical Nutrition, 54(6):963-969. AJCN
Westerterp KR. (2004). Diet induced thermogenesis. Nutrition & Metabolism, 1(1):5. PMC
Hall KD. (2010). Predicting metabolic adaptation, body weight change, and energy intake in humans. American Journal of Physiology – Endocrinology and Metabolism, 298(3):E449-E466. PMC
Shcherbina A, Mattsson CM, Waggott D, et al. (2017). Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. Journal of Personalized Medicine, 7(2):3. PMC
Apple. Get the most accurate measurements using your Apple Watch. Apple Support
Jensen MD, Ryan DH, Apovian CM, et al. (2014). 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults. Circulation, 129(25 Suppl 2):S102-S138. PMC
CDC. Steps for Losing Weight. CDC
Slater GJ, Dieter BP, Marsh DJ, et al. (2019). Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Frontiers in Nutrition, 6:131. PMC
Iraki J, Fitschen P, Espinar S, Helms E. (2019). Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports, 7(7):154. PMC
Morton RW, Murphy KT, McKellar SR, et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6):376-384. PMC
Tudor-Locke C, Aguiar EJ, Han H, et al. (2019). Walking cadence (steps/min) and intensity in 21–40 year olds: CADENCE-adults. International Journal of Behavioral Nutrition and Physical Activity, 16:8. PMC
Herrmann SD, Willis EA, Ainsworth BE, et al. (2024). 2024 Adult Compendium of Physical Activities: a third update of the energy costs of human activities. Journal of Sport and Health Science, 13(1):6-12. PMC
U.S. Department of Agriculture. FoodData Central — the values on our food pages. USDA

Calculate Your Exact Calorie Target

AI Food Coach calculates your TDEE from your profile and, with Apple Health or Health Connect, from the energy your watch records — plus TEF from every meal you log. Your calorie target updates as you eat, move, and weigh in. On your wrist, it is a calorie counter for Apple Watch and a calorie counter for Wear OS and Galaxy Watch.