The short answer
Calorie needs vary a lot from person to person. As a rough guide, the 2020 to 2025 edition of the US Dietary Guidelines estimated that most adult women need about 1,600 to 2,400 calories a day and most adult men about 2,000 to 3,000, depending on age, size and activity.
To estimate your number, calculate your resting needs with the Mifflin-St Jeor equation, then multiply by an activity factor. The result is an estimate. Your weight over the following few weeks tells you whether it is right.
Step 1: your resting needs (BMR)
Your basal metabolic rate (BMR) is the energy your body uses at rest to breathe, circulate blood and keep warm. The Mifflin-St Jeor equation is one of the more accurate estimates for most adults:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Example: a 30-year-old woman, 65 kg, 165 cm tall: (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1,031 − 150 − 161 = about 1,370 calories.
Step 2: add your activity level
Multiply your BMR by the factor that matches your typical week:
| Activity level | Description | Multiply by |
|---|---|---|
| Sedentary | Desk job, little exercise | 1.2 |
| Lightly active | Light exercise 1 to 3 days a week | 1.375 |
| Moderately active | Moderate exercise 3 to 5 days a week | 1.55 |
| Very active | Hard exercise 6 to 7 days a week | 1.725 |
| Extremely active | Physical job plus hard training | 1.9 |
For the example above, lightly active: 1,370 × 1.375 = about 1,880 calories a day to maintain weight. If sedentary, about 1,640. If moderately active, about 2,120.
A 40-year-old man, 80 kg, 180 cm, moderately active: BMR = 800 + 1,125 − 200 + 5 = 1,730, × 1.55 = about 2,680.
This total is often called TDEE (total daily energy expenditure) or maintenance calories.
Step 3: adjust for your goal
- Maintain weight: eat around your TDEE.
- Lose weight: a deficit of about 300 to 500 calories a day is a common, sustainable starting point. It typically leads to a loss of about 0.25 to 0.5 kg (0.5 to 1 lb) a week at first.
- Gain weight or build muscle: a surplus of about 250 to 500 calories, with enough protein and strength training.
Avoid very large deficits. They are hard to sustain, can cause muscle loss and fatigue, and make it difficult to get enough nutrients.
Why the numbers are only a starting point
- Formulas are averages. Real metabolism can differ by a few hundred calories from the estimate.
- People misjudge activity. Most people overestimate how active they are.
- Food labels and trackers are approximate.
- Your body adapts. As you lose weight, you need fewer calories, so targets need updating.
The practical method: follow your estimate for two to four weeks, weigh yourself at the same time a few days a week, and adjust by 100 to 200 calories if the trend is not what you want.
Quality matters as well as quantity
The same number of calories can leave you full or hungry. Meals built around:
- Vegetables, fruit and wholegrains (high in fibre),
- Protein (eggs, fish, poultry, beans, lentils, dairy, tofu),
- Healthy fats in sensible amounts,
tend to keep you full for longer than sugary drinks, refined snacks and many ultra-processed foods. Our healthy eating meal plans show what this looks like in practice.
Who should get personal advice
Speak to a doctor or registered dietitian before changing your diet significantly if you:
- Are pregnant or breastfeeding.
- Have diabetes, kidney disease, heart disease or another long-term condition.
- Take medicines affected by diet, including weight-loss drugs.
- Have a history of eating disorders.
- Are under 18 or over 65 and planning to lose weight.
Key takeaways
- Most adults need roughly 1,600 to 3,000 calories a day.
- Estimate yours with Mifflin-St Jeor and an activity factor.
- For weight loss, a 300 to 500 calorie daily deficit is a sensible start.
- Treat the number as an estimate and adjust from real results.
This article is general information, not medical or dietary advice. Speak to a health professional about your own needs.