How Many Calories Do I Need a Day?

🎧 Podcast · Pavel

How many calories a day do you need to keep your weight, lose weight or build muscle? It depends on your sex, age, height, weight and how active you are. Daily calorie needs often differ by several hundred calories between two people of the same weight. That is why we built a free calorie calculator that works out your calorie target, basal metabolic rate, body mass index and your protein, fat and carbohydrate amounts in seconds.

What the calculator works out

Daily calorie needs in kilocalories and kilojoules for your goal: lose weight, stay fit or build muscle.
Basal metabolic rate (BMR): the energy your body uses at complete rest.
Energy use with activity at six levels, from a sedentary lifestyle to physical work plus daily training.
Protein, carbohydrates, fat and fibre in grams and percent.
Body mass index (BMI) with a colour scale from underweight to obesity.
Waist-to-hip ratio (WHR) and body shape (pear, balanced, apple) if you enter your measurements.
Suggested water intake per day.

How daily calorie needs are calculated

First we work out your basal metabolic rate with the Mifflin-St Jeor equation, one of the most accurate for healthy adults:

men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5;
women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161.

Then we multiply the result by an activity factor from 1.2 (sedentary) to 1.9 (very active). To lose weight we subtract 15%; to build muscle we add 10%. If your BMI is outside the normal range and your body fat percentage is known, we use the Katch-McArdle equation, which accounts for lean body mass and is more accurate in that case. The calculator can also estimate body fat from your neck, waist and hip measurements using the US Navy formula.

Example: how many calories a day for a woman and a man

A woman, 30, 168 cm, 65 kg, exercising 1–3 times a week: BMR 1,389 kcal and about 1,910 kcal a day to stay fit, of which 119 g protein, 224 g carbohydrates, 59 g fat and 27 g fibre.

A man, 40, 182 cm, 95 kg, exercising 3–5 times a week, aiming to lose weight: from his measurements the calculator estimates about 25% body fat, switches to Katch-McArdle and suggests about 2,520 kcal a day.

Your numbers may be very different: calculate your own calorie needs with the calculator.

Protein, fat and carbohydrates: which split to choose

The calculator splits your calories into macronutrients by goal:

stay fit: protein 25%, carbohydrates 47%, fat 28%;
lose weight: protein 28%, carbohydrates 43%, fat 29%; more protein helps you keep muscle;
build muscle: protein 25%, carbohydrates 49%, fat 26%; more energy for training.

Grams are based on 4 kcal per gram of protein and carbohydrate and 9 kcal per gram of fat. We suggest 14 g of fibre per 1,000 kcal.

What to do with your result

Keep a food diary for 2–3 weeks and compare what you actually eat with the target.
Weigh yourself once a week at the same time and watch the trend, not single days.
If your weight does not change as expected, adjust your target by 100–200 kcal.
Recalculate when your weight changes by 3–5 kg or your activity changes.

The calculator gives a guide for healthy adults. If you are pregnant, have a medical condition or train professionally, ask a doctor or dietitian.

Could your website use a calculator?

An interactive calculator is one of the best ways to make a website bring in customers on its own: people search Google for a “calculator”, stay on the page longer and leave their contact details to get an exact offer. The same approach works for a price calculator for a construction or renovation company, a loan or leasing calculator, a product configurator for an online store, or an enquiry form that shows the price instantly.

We build these tools: price quote and measurement report software, custom web applications, calculators for WooCommerce stores and improvements to existing websites. Write to us and we will work out which tool would bring your business more enquiries.