How Many Calories Should I Eat? A Step-by-Step Answer
"How many calories should I eat?" is the most asked question in nutrition — and the most personal, because the answer depends on your weight, height, age, sex, activity and goal. A 25-year-old man who trains daily needs twice as many calories as a 60-year-old woman who sits at a desk, and the same person needs different calories for losing, maintaining or gaining weight.
This guide gives a step-by-step answer: how to calculate your maintenance calories (TDEE), how to adjust them for your goal, and worked examples for three different people, so you can see exactly how the numbers are reached. It is the foundation that every other nutrition decision rests on — and it is simpler than the diet industry makes it look.
Use the calculator
Start with your own numbers: try our calorie calculator, TDEE calculator to work out your figures before applying anything on this page. The worked examples below use round numbers so you can follow the maths; the calculators use your real weight, height, age and goal.
Related reading: How Much Protein Per Day? The Evidence-Based Ranges, What Are Macros? Protein, Carbs and Fat Explained Simply, How to Lose Weight Safely — A Practical, Evidence-Based Guide. You can also browse the full guides section for the rest of the series.
The key points
Step 1: calculate your BMR with Mifflin-St Jeor. Basal metabolic rate is the energy your body uses at rest, and the Mifflin-St Jeor equation (Mifflin et al., 1990) is the most accurate widely used formula: men, BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; women, BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161. It is an estimate, not a measurement — individual BMR varies by about ±10% — but it is the best starting point available without a laboratory.
Step 2: multiply by your activity level to get TDEE. Total daily energy expenditure is BMR times an activity multiplier: 1.2 for sedentary (desk job, little exercise), 1.375 for lightly active (light exercise 1–3 days a week), 1.55 for moderately active (moderate exercise 3–5 days), 1.725 for very active (hard exercise 6–7 days), and 1.9 for extremely active (physical job plus hard training). Most people overestimate their activity — be honest, and start with the lower multiplier if you are unsure.
Step 3: adjust for your goal. To lose weight, subtract 300–500 kcal from TDEE (a deficit that produces about 0.3–0.5 kg a week). To maintain, eat at TDEE. To gain muscle, add 200–300 kcal. The adjustment is the goal; the TDEE is the anchor. And the safety floors apply to the result: never plan a target below 1,200 kcal a day for women or 1,500 kcal a day for men without medical supervision.
Step 4: test it for two weeks, then adjust. The calculated TDEE is an estimate, and the only way to know your real maintenance is to eat a consistent amount for two weeks and watch the weight trend. If the weight is stable, the intake is your maintenance. If it falls, the intake is below maintenance; if it rises, it is above. Adjust by 100–200 kcal at a time, based on the trend — never on a single day's weigh-in.
Activity is the variable you control most. The difference between sedentary (1.2) and moderately active (1.55) is 29% of BMR — about 400–500 kcal a day for most adults. That is why two people of the same size can need very different calories, and why adding daily steps or a few training sessions changes the answer more than any diet tweak. If your calculated TDEE seems low, the fix is usually more activity, not less food.
Age and sex are in the formula for a reason. BMR falls by 5 kcal a year with age, and the women's formula subtracts 161 kcal relative to the men's — reflecting differences in average muscle mass. These are population averages, and individual variation is large: a muscular woman can have a higher BMR than a sedentary man of the same weight, and the formula does not know that. Use the formula as a starting point, and let the two-week test correct it.
At a glance
| Person | BMR | Activity | TDEE | Lose (−500) | Maintain | Gain (+250) |
|---|---|---|---|---|---|---|
| Woman, 35, 70 kg, 165 cm, lightly active | 1,395 kcal | 1.375 | 1,918 kcal | 1,418 kcal | 1,918 kcal | 2,168 kcal |
| Man, 30, 85 kg, 180 cm, moderately active | 1,830 kcal | 1.55 | 2,837 kcal | 2,337 kcal | 2,837 kcal | 3,087 kcal |
| Woman, 55, 65 kg, 160 cm, sedentary | 1,214 kcal | 1.2 | 1,457 kcal | 1,200 kcal* | 1,457 kcal | 1,707 kcal |
| Man, 45, 90 kg, 178 cm, very active | 1,793 kcal | 1.725 | 3,093 kcal | 2,593 kcal | 3,093 kcal | 3,343 kcal |
*The 55-year-old woman's 500 kcal deficit would give 957 kcal, which is below the 1,200 kcal floor — so her deficit is capped at 257 kcal, giving a target of 1,200 kcal. The floor is a safety limit, not a suggestion.
The formula behind it
The full calculation, worked through for the 35-year-old woman in the table: BMR = 10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031 − 175 − 161 = 1,395 kcal. She is lightly active, so TDEE = 1,395 × 1.375 = 1,918 kcal. To lose weight at about 0.5 kg a week, she subtracts 500 kcal: 1,918 − 500 = 1,418 kcal a day — above the 1,200 kcal floor for women, so it is a safe target. To gain muscle, she adds 250 kcal: 1,918 + 250 = 2,168 kcal a day.
The 55-year-old woman shows why the floors matter: BMR = 10 × 65 + 6.25 × 160 − 5 × 55 − 161 = 650 + 1,000 − 275 − 161 = 1,214 kcal; TDEE = 1,214 × 1.2 = 1,457 kcal. A 500 kcal deficit would give 957 kcal — far below the 1,200 kcal floor — so her deficit is capped: she eats 1,200 kcal a day (a 257 kcal deficit) and adds activity instead, aiming for a slower rate of about 0.25 kg a week. The alternative — eating 957 kcal — carries real risks and should only be done under medical supervision, if at all.
The protein that goes with these calories is 1.6–2.2 g/kg a day when losing weight or gaining muscle (1.2–1.6 g/kg for runners, 0.8 g/kg minimum for sedentary adults). At 70 kg and 1.8 g/kg, that is 126 g of protein a day, or 504 kcal — and the rest of the calories are carbohydrate and fat, in whatever ratio suits the person's training and preferences.
Your plan, step by step
- Calculate your BMR with Mifflin-St Jeor, using your weight, height, age and sex.
- Multiply by your activity level (be honest — most people overestimate) to get your TDEE.
- Adjust for your goal: −300–500 kcal to lose, TDEE to maintain, +200–300 kcal to gain.
- Check the result against the safety floors: never below 1,200 kcal (women) or 1,500 kcal (men) without medical supervision.
- Eat that amount consistently for two weeks, watch the weight trend, and adjust by 100–200 kcal at a time.
How to use this guide
Use this guide as the starting point for every nutrition decision, and use the calculators for your own numbers. The worked examples show the method; the calculators apply it to your weight, height, age and goal. Do not copy someone else's calorie target — a target that is right for a 30-year-old man who trains daily is wrong for a 55-year-old woman who sits at a desk, and the difference is not willpower, it is arithmetic.
Re-calculate every 4–5 kg of weight change, and every time your activity changes significantly. A TDEE calculated at 90 kg is wrong at 82 kg, because a lighter body burns fewer calories — and the deficit that worked at the start of a diet disappears as the weight falls. The two-week test is the correction: eat consistently, watch the trend, and adjust. The formula gives you the starting point; the scale gives you the truth.
What this guide does NOT tell you
Mifflin-St Jeor is an estimate with a typical error of about ±10% — for a TDEE of 2,000 kcal, that is ±200 kcal, which is the difference between losing and maintaining. Body composition matters and the formula does not know it: a muscular person burns more than the formula predicts, and a person with very high body fat burns less. The activity multipliers are also estimates, and most people overestimate their activity by one level.
This guide is general information, not medical advice. It does not diagnose or treat anything, and it cannot tell you what to eat for your specific health situation. Anyone with a medical condition, an eating disorder, diabetes, kidney disease or any condition affected by diet should follow a clinician's or dietitian's plan rather than a general guide — and no one should eat below the safety floors without medical supervision.
Frequently asked questions
How many calories should I eat a day?
It depends on your weight, height, age, sex, activity and goal — there is no single number. As a rough guide, a moderately active woman needs about 1,800–2,200 kcal a day and a moderately active man about 2,400–2,800 kcal, but the only accurate answer comes from calculating your TDEE with Mifflin-St Jeor and testing it for two weeks. Use the calorie calculator on this site with your own numbers, and adjust by 100–200 kcal based on the weight trend.
How many calories should I eat to lose weight?
Your TDEE minus 300–500 kcal a day, which produces about 0.3–0.5 kg of loss a week. For a woman with a TDEE of 1,918 kcal, that is a target of about 1,418 kcal; for a man with a TDEE of 2,837 kcal, about 2,337 kcal. Never go below 1,200 kcal a day (women) or 1,500 kcal a day (men) without medical supervision — if the maths lands below the floor, shrink the deficit and add activity instead.
How do I calculate my maintenance calories?
Calculate your BMR with Mifflin-St Jeor (men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5; women: the same minus 161 instead of plus 5), then multiply by your activity level (1.2 sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active). The result is your TDEE — your maintenance. Test it by eating that amount for two weeks: if your weight is stable, the calculation was right; if it moves, adjust by 100–200 kcal.
Why is my TDEE lower than I expected?
Usually because activity was overestimated — most people choose a multiplier one level too high — or because body composition is lower in muscle than the formula assumes. The formula also has a ±10% error, so a calculated TDEE of 2,000 kcal could truly be 1,800–2,200 kcal. The fix is the two-week test: eat the calculated amount consistently, watch the trend, and adjust. If the weight is stable at the calculated TDEE, the calculation was right, whatever it felt like it should have been.
Should I eat more on days I exercise?
It depends on the approach: some people eat the same amount every day, with the TDEE already including average activity; others eat more on training days and less on rest days, which matches expenditure more closely. Either works, provided the weekly average is right — the body responds to the weekly total, not to single days. The simpler approach (same target daily) is easier to follow, and for most people it produces the same result as the more complicated one.
Estimates only, not medical advice. Minimum safe intakes: 1,200 kcal/day women, 1,500 kcal/day men — consult a healthcare professional before a very-low-calorie diet.