Skip to main content

How Many Calories (Kilojoules) Do We Need in a Day?

Marie writes about health, well-being, writing and food. Marketing writer with 30 years experience in PR and advertising.

How many calories or kilojoules in one day?

How many calories or kilojoules needed in one day varies depending on your body type. Everyone has different food requirements depending on the amount of fuel needed to keep the body ticking correctly. The important thing is to eat enough calories to be healthy without putting on weight.

Food - we think about it, we buy it, we prepare it, we eat it and without it, we just don't survive. Food is a major part of our everyday lives but just how much of it do we need? What type do we need? What is good food? What is bad food? Too many questions to answer in just one hub so, for now, let's concentrate on how many calories (or kilojoules) we need to consume in one day. What will help us to achieve fat loss? Once you know this figure, which is different for each and everyone one of us, you will be able to determine how much you need to eat to either maintain your current weight, lose weight, or, lucky you, to put on weight.

Calories and Kilojoules - what's the difference?

Both are measurements for energy, food is usually measured in kilojoules and exercise in calories. If you want to convert kilojoules into calories then you divide kilojoules by calories.

Example: 1 Calorie = 4.184 kilojoules so 2000 kilojoules divided by 4.184 = 478 calories.

So, as both calories and kilojoules measure energy, you can use either to measure whether your intake of food is too much or too little for the energy you expend.

BMR, PAL, and BMI - what does it all mean?

What we eat every day determines our weight, health and overall mental state, literally, "we are what we eat". It's easy to surf the net to find all sorts of diets that may help you lose weight, but exactly how much should you eat to either lose weight or maintain the healthy weight you may be at now?

Whilst researching this topic I came across a site which suggested the average calorie intake should be between 1200 - 1500 calories per day. This is a very general figure as everyone has a different metabolism; it depends on age, whether you are male or female if there are any health issues and your current activity level.

Body Mass Index (BMI) measures whether you are the correct weight for your height. This measurement is not as accurate, so say some health professionals, as it may not give as accurate an indication as BMR xPAL.

OK, so let's be serious about being healthy. There are some calculations which need to be done to ascertain your individual body's status. This entails multiplying your Basal Metabolic Rate (BMR) by your Physical Activity Level (PAL).

BMR = amount of energy measured in calories just so your body can start each day.

PAL = the fuel required to power your body throughout the day, therefore -


By using the figure your BMR x PAL gives you it will give a good indication of the calories you are able to consume in a day. This figure will give you a guide as to how many calories your body needs to maintain, lose or gain weight.

It's easy to be tempted but an occasional treat is ok.

It's easy to be tempted but an occasional treat is ok.


We all know that women have different energy needs to men and this is the formula needed for us women, BMR x PAL (to work out your PAL use the Physical Activity Level table below) -

The formula - BMR = 655 + (9.6 x weight in kilos) + (1.8 x height in cm) - (4.7 x age in years)

eg: 655 + (9.6 x 70kilos) + (1.8 x 72cms) - (4.7 x 49) =

655 + 672 +129.6 - 230.3 = 1226.3 calories

Scroll to Continue

This figure is then multiplied by your PAL (see table below).

eg: 1226.3 calories x 1.55 (moderate) = 1990.77 calories needed per day

So, as a woman in her forties, who exercises moderately the above calculation shows she will need to consume nearly 2000 calories per day to maintain her weight. Obviously if she needs to lose weight then she will need to consume less calories per day.


Men will use a slightly different formula -

BMR = 66 + (13.75 x weight in kilos) + (5 x height in cm) - (6.8 x age in years)

eg: 66 + (13.75 x 95kilos) + (5 x 110cms) - (6.8 x 52) =

66 + 1306.25 + 550 - 353.6 = 1568.65 calories

This figure is then multiplied by your PAL (see table below).

eg: 1568.65 calories x 1.55 (moderate) = 2431.40 calories needed per day

So, as a man in his fifties, who exercises moderately the above calculation shows he will need to consume almost 2500 calories per day to maintain his weight. Once again, if he needs to lose weight then he will need to consume fewer calories per day.


This model can be used for teenagers however it must be taken into account that teenagers are still growing and their hormones are raging so it stands to reason that more calories may be required for this age group (and it's probably the reason why they eat everything in sight!). Use these figures only as a guide for this age group.

Also, take into consideration younger children and the nutrition and calories they need. This model can again be used but a word of caution, remember that children are growing and need calories and good nutrition for healthy growth. It is NOT recommended to have children (or teenagers) put on a diet unless for medical reasons and with the supervision of a medically qualified dietician or nutritionist.

IMPORTANT NOTE: Do not exceed a weight loss of more than 0.91kg per week. More than this rate and you will burn muscle as well as fat, which is not healthy and may cause other problems. If you do want to start a diet and exercise program it is wise to seek the advice of a trained medical practitioner. The information contained in this article is a guide only.





Teenagers Can Learn to Cook.

Physical Activity Levels (pal)


Little or no exercise


Light exercise 1-3 days per week


Moderate exercise 3-5 days per week


Very active 6-7 days per week


Extremely active, physical job, train 2 x per day


Maintaining a Healthy Body

It isn't easy to work out your own personal calorie needs, is it? Just think, if it was easy many of us would be walking around looking perfect just like many celebrities. To look good and feel great it takes work and determination.

These formulae and figures are for people who are serious about being healthy, losing weight and keeping it off; they read labels, watch the types of fats they consume, keep away from trans fats and watch the number of different sugars they eat. For seriously obese people these formulas are a good way to understand just how much they are eating and may give them the incentive to begin a weight loss program.

As well as the food we consume we need to take into account the type of drinks we have every day. Coffee, soft drinks, milk, flavoured mineral waters, sports water and alcohol all contain kilojoules and how many of these drinks you consume each day will add to your daily tally. One of the best ways to keep calories down, and help keep hunger at bay, is to drink water. The average requirement for an adult is 8 glasses per day, but again, it depends on your own personal circumstances.

What are carbohydrates, proteins, fats? Many people who follow a good diet and exercise regime know all about what they put into their bodies. There are many more questions to be answered and these are answered here -

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2010 Maria Giunta


Maria Giunta (author) from Sydney, Australia on April 02, 2012:

Thanks for your comment and reading Peter and it's never too late. We hubbers appreciate comments at any time.

Peter Nisbet on April 02, 2012:

A bit late for this after 2 years, by why use men at 3 ft 7 inches (110 cm) and women even smaller? Are these movies I am watching in the UK ehnhanced to show Americans larger than they really are, or was Alan Ladd genuinely representative of the big American male?

Maria Giunta (author) from Sydney, Australia on January 21, 2011:

Hi Peg, thanks for commenting and for your praise. Checked out your site so I'm looking forward to reading about your dogs and your many jobs.

Peg Cole from North Dallas, Texas on January 21, 2011:

Well this settles a discussion I had with the hubby last week about how many calories a body needs. Ha Ha. I was right. Very informative article and nicely written.

Maria Giunta (author) from Sydney, Australia on November 04, 2010:

Hi Gals, thanks for dropping by my hub. This is took quite a lot of research and I also learnt a lot from it. Thanks for your support.

Susan Hazelton from Northern New York on November 01, 2010:

Great information and so much of it. Voted up, useful and bookmarked. I'll have to read again a few times to digest it all.

Maria Giunta (author) from Sydney, Australia on October 09, 2010:

Hi hpw, nice to hear from you. Hope you are able to use some of these tips.

hubpageswriter on October 07, 2010:

This is a good hub. There are different types of foods for different calorie count and it is a good source of gauge for a more healthy living.

Maria Giunta (author) from Sydney, Australia on May 31, 2010:

I hope so, MaryRenee. Thanks for reading and becoming a fan.

MaryRenee on May 31, 2010:

great hub Marie! everyone could benefit from this inform ation. :)

Maria Giunta (author) from Sydney, Australia on March 25, 2010:

Thank Tn, in USA and Australia especially, the two most obese countries in the world. Thanks for passing by.

TnFlash from Tampa, Florida on March 25, 2010:

Great Hub! This is needed information for everyone who cares about their health and maintaining their weight. Good Work!

Maria Giunta (author) from Sydney, Australia on March 24, 2010:

Glad it's helpful Richard, thanks for passing by my site.

Richard Armen on March 24, 2010:

This is a ton of great info...thanks.

Maria Giunta (author) from Sydney, Australia on March 23, 2010:

Thanks ladyjane1, I enjoyed video too. Jb, yes it is complicated but if it was easy we'd all be skinny! Thanks for comments both of you.

jb1310 on March 23, 2010:

thanks for the info - its very complicated but according to this I can have approx 1900 calories a day - seems a lot. Now need to work out how many calories are in the food to eat!!

ladyjane1 from Texas on March 23, 2010:

great info loved the video.

Maria Giunta (author) from Sydney, Australia on March 23, 2010:

Lady_E - oh yes good ol' chocolate. I must admit I'm not good at counting them either but now I know how I might give it a go once!

De Greek - it is a lot to digest in one go.

Pamela - hope all the info helps.

Thanks for commenting everyone.

Pamela Oglesby from Sunny Florida on March 23, 2010:

This is an excellent with great information. Thanks for the charts and the info.

De Greek from UK on March 23, 2010:

I have printed this out, as I cannot digest it in situ :-))

Good stuff and very useful, thank you :-)

Elena from London, UK on March 23, 2010:

Very interesting and enlightening Hub. I must confess, I don't ever count calories. I just eat or pick up a chocolate bar anytime my stomach shouts out "Hey Elena, it's getting quiet in here".

Best Wishes.

Related Articles