How many calories should I eat a day: chart by sex and age, formula and examples for weight loss

The question "how many calories should I eat a day" has two answers. The quick one is a reference figure for someone of your sex, age and activity level, and you will find it in the two charts below. The precise one is your total daily energy expenditure (TDEE): the sum of what you burn at rest, what you burn by moving and what you use to digest food. That one is estimated with a formula and fine-tuned by watching how your body weight responds.

How many calories should a woman eat a day? Chart by age and activity

EFSA (the European Food Safety Authority) publishes the average energy requirements of healthy adults. It calculated them with the Henry equation for resting energy expenditure, the heights measured in 13 national surveys from EU countries and the body weight that corresponds to a BMI of 22, and multiplied the result by a physical activity level (PAL) of 1.4 for a sedentary lifestyle, 1.6 for a moderately active one and 1.8 for an active one. EFSA gives the values in megajoules; here they are converted to kilocalories and rounded to the nearest ten, so treat them as approximate.

How many calories should a man eat a day? Chart by age and activity

This is the same EFSA method, using the average heights of European men and a BMI of 22. Notice two things: the gap between a sedentary and an active lifestyle is around 600-700 kcal a day, far more than the difference between age 30 and age 59; and from 60 onwards energy needs drop noticeably. EFSA did not calculate values for adults over 80 because anthropometric data for that group were lacking.

How to calculate your calories: the Mifflin-St Jeor formula

The charts describe an average person. If you are 1.55 m or 1.90 m tall, or weigh a lot more or less than the reference, your figure may be different. To fine-tune it, calculate your resting energy expenditure with the Mifflin-St Jeor equation (1990), which was derived by measuring 498 adults aged 19 to 78, of normal weight and with obesity, using indirect calorimetry. All you need is your weight (kg), height (cm) and age:

• Men: (10 x weight) + (6.25 x height) - (5 x age) + 5
• Women: (10 x weight) + (6.25 x height) - (5 x age) - 161
• How accurate it is: in the systematic review by Frankenfield et al. (2005) for the American Dietetic Association, it was the equation that most often came within 10% of measured expenditure, in people with and without obesity, although with sizeable errors in some individuals
• Why it is only a starting point: according to the review by Fernández-Verdejo and Galgani (2022), different equations can disagree by up to about 400 kcal a day for resting expenditure and about 550 kcal for total expenditure

Multiply by your activity level (TDEE)

The result of the formula is what you would burn at rest. To estimate your maintenance calories you multiply it by an activity factor. The factors in the chart are the conventional multipliers used by most calculators: they do not come from the Mifflin study and they are approximate. Nor can they be compared one to one with the EFSA PAL, which is applied to a different resting equation. Be careful not to overestimate: if you have a desk job and train three hours a week, the sensible move is to start at the light level and correct it with real data.

Example 1: woman, 35 years old, 165 cm, 70 kg, lightly active

She works in an office and goes to the gym or out walking two days a week. Resting expenditure: (10 x 70) + (6.25 x 165) - (5 x 35) - 161 = 700 + 1031 - 175 - 161 = 1395 kcal. Maintenance with light activity: 1395 x 1.375 = about 1920 kcal a day. If she wants to lose weight, her target would be about 1420-1620 kcal (300-500 kcal less). If she wants to build muscle while doing strength training, about 2120-2220 kcal. Compare that with the EFSA chart: for her age it ranges from ~1820 kcal (sedentary) to ~2080 kcal (moderately active), so her calculation falls within the expected range.

Example 2: man, 40 years old, 178 cm, 85 kg, moderately active

He does strength training or goes running four days a week. Resting expenditure: (10 x 85) + (6.25 x 178) - (5 x 40) + 5 = 850 + 1112.5 - 200 + 5 = about 1768 kcal. Maintenance with moderate activity: 1768 x 1.55 = about 2740 kcal a day. To lose weight: about 2240-2440 kcal. To build muscle: about 2940-3040 kcal. In the EFSA chart, a moderately active man aged 40 to 49 needs on average ~2560 kcal; he comes out somewhat higher because he weighs more than the BMI 22 reference.

How many calories to eat to lose weight

Subtract from your own maintenance, not from a magazine number. A deficit of 300-500 kcal a day is moderate: in the examples it means eating 16-26% less for her and 11-18% less for him. The 2013 AHA/ACC/TOS guideline for adults with overweight or obesity goes a little further and proposes a deficit of 500-750 kcal a day, or diets of 1200-1500 kcal for women and 1500-1800 kcal for men adjusted to body weight. On pace: with the classic rule (about 7700 kcal per kilo of fat), eating 500 kcal less a day works out at about 0.45 kg a week, but Thomas et al. (2013) showed that this rule overestimates weight loss over the medium term because, as you slim down, you also burn less. That is why it is worth recalculating once you have lost a few kilos. To see how much to eat with each deficit (and where your minimum is), use the calorie deficit calculator. To put a date on your goal, use the weight loss calculator and, if you are starting from scratch, read the beginner's guide to a calorie deficit.

• Woman in example 1: maintenance of ~1920 kcal; to lose weight, ~1420-1620 kcal
• Man in example 2: maintenance of ~2740 kcal; to lose weight, ~2240-2440 kcal
• If your result falls below about 1200 kcal (women) or 1500 kcal (men), do not cut further: move more or ask a professional for help

How many calories to eat to build muscle

Building muscle takes strength training, enough protein and, in general, a little more energy than you burn. How much more is not clear: the review by Slater et al. (2019) concludes that the ideal surplus is unknown and that the usual recommendations have never been validated in people who do resistance training. A prudent starting point is to add 200-300 kcal to your maintenance and watch the trend: if your weight climbs much faster than you expected, shrink the surplus. For protein, the meta-analysis by Morton et al. (2018) found no further gain in lean mass above about 1.6 g per kg a day. Work out your figures with the muscle gain calculator.

• Small surplus: maintenance + 200-300 kcal, as a starting point rather than a proven figure
• Protein: about 1.6 g per kg of body weight a day; more detail in how much protein you need a day
• Recomposition (losing fat and gaining muscle at the same time): maintenance or a very small deficit, enough protein and strength training

Why protein matters as much as the number

Once you have your figure, there is no need to obsess over every kcal. It is more useful to secure your protein: the review by Leidy et al. (2015) links diets with 1.2-1.6 g of protein per kg a day, and at least about 25-30 g per meal, to improvements in appetite and weight management, and the controlled studies it summarises show that they help preserve lean mass during a deficit. It is not magic, but it makes the deficit easier to live with.

Last step: adjust to your real weight, not to the formula

No equation knows how much you really move or what your body composition is like. The only way to find your number is to eat what the calculation says for 2-3 weeks, log what you eat and watch your weight trend (the weekly average, not a single day). If you wanted to lose weight and you are not losing, cut 150-200 kcal. If you are losing very fast, are constantly hungry or lack the energy to train, add a little. If you only want to know your resting expenditure, use the BMR calculator.

With Renzy you photograph your meals and the AI estimates their calories and macros; you review the estimate and correct it if needed, without weighing every ingredient. Then you compare your weight trend with your goal to see whether you are on track or should adjust your number.