Quick answer
How many calories do I need a day?
Most adult women need about 1,600 to 2,400 calories a day and most men about 2,000 to 3,000, depending on size and activity (Dietary Guidelines for Americans). Your own number is your maintenance calories (TDEE): your resting burn from the Mifflin-St Jeor equation multiplied by an activity factor. Eat about 10 to 20% below it to lose fat, or about 10% above it, with strength training, to gain muscle.
On this page
- How to use the calorie calculator
- How the calorie calculator works
- Activity level multipliers
- Calories for weight loss, maintenance and muscle gain
- Worked example
- BMR vs. TDEE: what’s the difference?
- How many calories should you cut to lose weight?
- Macronutrients: the quality of your calories
- Calories in common foods
- Common calorie counting mistakes
- Frequently asked questions
- Sources
How to use the calorie calculator
- Pick your units. Metric (kg, cm) or imperial (lb, ft and in).
- Enter your sex, age, height and weight. These drive your resting metabolic rate.
- Choose your activity level honestly. Most people with a desk job who train three or four times a week are “moderately active”, not “very active”.
- Choose a goal. Maintain, one of three weight loss speeds, or one of three muscle gain speeds.
- Optional: open Advanced Options to switch formula (Katch-McArdle if you know your body fat %) or show results in kilojoules.
- Press Calculate. You get your BMR, your maintenance calories and your daily target for the goal you chose.
How the calorie calculator works
Every calorie target comes from three steps. The calculator does all of them at once, but knowing what each one does tells you which input matters most.
- Resting burn (BMR). The calories your body uses at complete rest, estimated from your sex, age, height and weight. It is usually 60 to 70% of what you burn in a day.
- Maintenance (TDEE). BMR multiplied by an activity factor between 1.2 and 1.9. This is the amount that keeps your weight stable.
- Goal target. Maintenance adjusted for your goal: 10 to 25% less to lose fat, 10 to 20% more to gain muscle.
The three formulas
Mifflin-St Jeor (default)
The most accurate equation for healthy adults in head-to-head comparisons, and the one dietitians use by default.
Women: 10W + 6.25H − 5A − 161
Revised Harris-Benedict
The original 1919 equation, revised in 1984. Still common, and tends to read a little high for modern populations.
Women: 447.593 + 9.247W + 3.098H − 4.330A
Katch-McArdle
Works from lean body mass instead of total weight, so it is the best choice when you know your body fat percentage from a reliable measurement.
LBM = W × (1 − body fat %)
Key
W = weight in kg, H = height in cm, A = age in years, LBM = lean body mass in kg. Imperial inputs are converted to metric before the maths runs.
Activity level multipliers
The activity factor is the biggest variable in the result, and the one people most often overestimate. Pick the row that describes a normal week, not your best one.
| Activity level | Multiplier | What it looks like |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise 1–3 days a week, or a job with some walking |
| Moderately active | 1.55 | Exercise 3–5 days a week |
| Very active | 1.725 | Hard training 6–7 days a week |
| Super active | 1.9 | Physical job plus training, or athlete-level volume |
Calories for weight loss, maintenance and muscle gain
The goal menu scales your maintenance calories by a percentage, so the adjustment grows with your size. Here is what each option means in practice.
| Goal | Adjustment | Typical result |
|---|---|---|
| Aggressive weight loss | −25% | Fast loss; hard to sustain for more than a few weeks |
| Weight loss | −20% | About 0.5–1 kg (1–2 lb) a week for most people |
| Mild weight loss | −10% | Slow, easy to stick to; good when already fairly lean |
| Maintain | 0% | Weight stays stable |
| Lean muscle gain | +10% | Slow gain with minimal fat, for trained lifters |
| Muscle gain | +15% | Faster gain, some fat alongside |
| Aggressive mass gain | +20% | For hard gainers and beginners who struggle to eat enough |
A useful rule of thumb from weight change research: a daily deficit of about 500 calories produces roughly 0.5 kg (1 lb) of loss a week at first, then slows as your weight and burn come down. That is why the target needs recalculating as you go.
Worked example
Here is the maths for two people who both exercise three to five times a week (activity factor 1.55), using Mifflin-St Jeor.
| Person | BMR | Maintenance | Weight loss (−20%) |
|---|---|---|---|
| Woman, 30, 165 cm, 65 kg | 1,370 kcal | 2,124 kcal | 1,699 kcal |
| Man, 30, 178 cm, 80 kg | 1,768 kcal | 2,740 kcal | 2,192 kcal |
Same age, same training, yet their maintenance calories are more than 600 apart. That gap is why generic advice like “eat 1,500 calories” fails so many people, and why working from your own numbers is worth the two minutes.
BMR vs. TDEE: what’s the difference?
Your basal metabolic rate (BMR) is the energy your body burns at complete rest: breathing, circulation, brain activity and keeping warm. Your total daily energy expenditure (TDEE) adds the calories from walking, exercise, fidgeting and digesting food.
TDEE is the number that matters for weight change, because it reflects a normal day. Eat below it and you lose weight; eat above it and you gain. Never use BMR as an eating target: it is what you would burn lying in bed all day. Use the BMR calculator or TDEE calculator if you want either number on its own.
How many calories should you cut to lose weight?
A deficit of around 500 calories a day, or 15 to 20% below maintenance, is the usual starting point. It is large enough to see steady progress and small enough to keep training, sleeping and concentrating normally.
- Don’t go below about 1,200 calories (women) or 1,500 (men) without medical supervision. Below that it is hard to meet protein and micronutrient needs.
- Keep protein high. Around 1.6 g per kg of body weight helps protect muscle while you lose fat. The protein calculator gives you a gram target.
- Plan the deficit backwards from a date with the calorie deficit calculator if you have a goal weight in mind.
Macronutrients: the quality of your calories
Calories decide whether your weight goes up or down. Macronutrients decide how much of that change is fat and how much is muscle, and how full you feel along the way.
Protein: 4 kcal/g
Builds and protects muscle and is the most filling macro. Aim for 1.6–2.2 g per kg of body weight when training.
Carbohydrate: 4 kcal/g
The main fuel for hard exercise and the brain. Choose mostly high-fibre sources such as oats, beans, fruit and potatoes.
Fat: 9 kcal/g
Needed for hormones and vitamin absorption. Keep it to at least 20% of calories, even when cutting.
Split them for you
The macro calculator turns your calorie target into grams of protein, carbs and fat.
Calories in common foods
Average values per 100 g (3.5 oz), rounded, from standard food composition tables.
| Food | Calories | Protein | Mostly |
|---|---|---|---|
| Chicken breast, cooked | 165 kcal | 31 g | Protein |
| Salmon, raw | 208 kcal | 20 g | Protein, fat |
| Egg (1 large, 50 g) | 72 kcal | 6 g | Protein, fat |
| White rice, cooked | 130 kcal | 2.7 g | Carbs |
| Rolled oats, dry | 379 kcal | 13 g | Carbs |
| Avocado | 160 kcal | 2 g | Fat |
| Almonds | 579 kcal | 21 g | Fat |
| Broccoli | 34 kcal | 2.8 g | Fibre |
| Banana | 89 kcal | 1.1 g | Carbs |
| Apple | 52 kcal | 0.3 g | Carbs |
Common calorie counting mistakes
- Underestimating intake. Studies consistently find people under-report what they eat by 20 to 30%. A cheap kitchen scale fixes most of it.
- Overestimating activity. Choosing “very active” for four gym sessions a week can add 300+ phantom calories. When unsure, pick the lower level.
- Forgetting liquid calories. Juice, alcohol, sugary coffee drinks and cooking oil add up quickly and rarely get logged.
- Weekend drift. Five careful days and two loose ones can erase the whole week’s deficit.
- Never recalculating. Your needs fall as you lose weight. Re-run the calculator every 5 kg (10 lb) or when your routine changes.
Frequently asked questions
How many calories should I eat to lose weight?
Start about 500 calories below your maintenance number, or 15 to 20% below it. For most people that works out to roughly 0.5 kg (1 lb) of loss a week. Go slower if you are already lean, and recalculate every 5 kg (10 lb) or so, because a lighter body burns less.
How fast should I lose weight?
A sustainable rate is 0.5 to 1% of body weight a week, which for most people is 0.5 to 1 kg (1 to 2 lb). Losing faster than that tends to cost muscle, makes hunger harder to manage, and is more likely to rebound.
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is what your body burns at complete rest just to keep you alive. TDEE (total daily energy expenditure) adds everything else: walking, exercise, work and digesting food. TDEE is your maintenance calories, and it is the number to build a diet from.
How accurate is this calorie calculator?
For most healthy adults, the Mifflin-St Jeor equation predicts resting burn within about 10% of a lab measurement. The bigger source of error is the activity level you pick. Treat the result as a starting point, track your weight for two to three weeks, and adjust by 100 to 200 calories if it is not moving the way you expect.
Is 1,200 calories a day enough?
For most adults it is too low to sustain. 1,200 calories is often quoted as a floor for women and 1,500 for men, because below that it becomes hard to get enough protein, vitamins and minerals from food. Very low calorie diets should only be done with medical supervision.
Should I eat back the calories I burn exercising?
Not if you already picked an activity level that includes your training, because the calculator has counted it. Fitness trackers also tend to overestimate exercise burn, so if you do eat some back, eat back half at most.
What if I hit a plateau?
Plateaus are normal. As you lose weight your BMR falls, and many people move less without noticing. Recalculate at your new weight, tighten up tracking for a week (weigh foods, count drinks and oils), and add daily steps before cutting food further.
Do I need to count calories forever?
No. Counting for a few weeks teaches you what portions of your usual foods look like. Most people can then move to a looser approach, such as consistent meals or a meal plan built to their target, and only go back to tracking if progress stalls.
How do I convert calories to kilojoules?
Multiply calories (kcal) by 4.184. A 2,000 kcal day is about 8,370 kJ. Choose Kilojoules in Advanced Options and the calculator converts every result for you.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990.
- Frankenfield D, et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc, 2005.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr, 1984.
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011.
- U.S. Department of Agriculture and HHS. Dietary Guidelines for Americans, 2020–2025.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Weight management.
This calculator gives estimates for healthy adults and is for information only. It is not a diagnosis or a substitute for advice from a doctor or registered dietitian.