If you've ever picked up a packaged snack, flipped it over and looked at the nutrition label, you might have noticed a percentage of an adult's reference intake. In the UK, these percentages are typically calculated using a daily reference intake of 2,000 calories.
But where does that number come from? And, more importantly, does it actually apply to you?
For decades, this 2,000-calorie figure has been used as a standard reference for food labelling. It makes comparing nutritional information easier, so it serves a useful purpose. But if you've ever wondered whether that number actually reflects your own energy needs, the short answer is: well, it depends.
The truth is that the standard 2,000-calorie benchmark is a convenient reference, not a personal recommendation. It doesn't take into account your age, height, weight or daily routine.
To get a better idea of how much energy your body needs, we can turn to a couple of useful formulas.
Step 1: Your Body at Rest – Basal Metabolic Rate (BMR)
Before figuring out how many calories you burn while walking, working or exercising, you need to know how much energy your body requires just to stay alive. This baseline is known as your Basal Metabolic Rate (BMR).
Think of your BMR as the energy your body consumes when you are resting completely. Even when you aren't doing anything, your body is working hard. Your heart is pumping blood, your lungs are breathing, your kidneys are filtering waste, and your brain is firing signals. All these automatic life-support systems require fuel.
Measuring BMR directly requires specialised laboratory conditions, so scientists have developed formulas to estimate how much energy your body uses at rest.
One of the most widely used and well-regarded methods is the Mifflin-St Jeor equation.
Developed in the 1990s, this formula remains a useful way to estimate resting energy needs using four simple variables: weight, height, age and biological sex.
The equations differ for men and women to reflect average differences in body composition and energy requirements.
For men:
BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women:
BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
As you can see from the maths, your estimated baseline energy needs vary with your physical characteristics. If you weigh more or are taller, the formula generally predicts a higher BMR because there is more body tissue to support. As you get older, it predicts slightly lower resting energy needs.
This helps explain why a tall 20-year-old athlete and a petite 65-year-old grandmother shouldn't automatically rely on the same generic 2,000-calorie recommendation.
Of course, these calculations are estimates. Two people of the same age, height, weight and sex can still have different energy requirements. The formula gives us a useful starting point, not an exact measurement.
Step 2: Factoring in Movement – Total Daily Energy Expenditure (TDEE)
Your BMR is only the starting point. Unless you spend the entire day resting, your body will use additional energy through everyday movement, exercise and even digesting food.
To get a better estimate of your daily energy requirements, we need to look at your Total Daily Energy Expenditure (TDEE).
Your TDEE is the total amount of energy your body uses over 24 hours.
One common way of estimating it is to multiply your resting energy needs by an activity factor, based on your overall lifestyle.
| Activity Level | Description | Approximate Multiplier |
|---|---|---|
| Sedentary | Mostly sitting, little exercise | BMR × 1.2 |
| Lightly Active | Light exercise or sports 1–3 days a week | BMR × 1.375 |
| Moderately Active | Moderate exercise or sports 3–5 days a week | BMR × 1.55 |
| Very Active | Hard exercise or sports 6–7 days a week | BMR × 1.725 |
| Extremely Active | Intense daily exercise and a highly physical lifestyle | BMR × 1.9 |
These multipliers are approximations, not fixed scientific rules.
And activity doesn't always fit neatly into categories. Someone who walks 15,000 steps every day but never visits a gym might use more energy than someone who exercises three times a week but spends the rest of their time sitting at a desk.
Another approach is to start with a sedentary baseline and account for additional movement and exercise separately. This can be particularly useful when your activity levels vary considerably from one day to the next.
Whichever approach you use, the aim is the same: to estimate how much energy your body needs over the course of a typical day.
Step 3: Let's Put Some Numbers Into Practice
Formulas are easier to understand with a real example.
Let's imagine a 35-year-old woman who is 165 cm tall, weighs 70 kg and has a mostly sedentary lifestyle.
First, we calculate her estimated BMR using the Mifflin-St Jeor equation:
BMR = (10 × 70) + (6.25 × 165) − (5 × 35) − 161
That works out to approximately 1,395 calories per day.
This is the estimated energy her body needs at rest, before accounting for her normal daily activities.
Now let's calculate her TDEE using the sedentary activity multiplier of 1.2:
TDEE = 1,395 × 1.2 = 1,674 calories per day
So, her estimated daily energy requirement is around 1,674 calories to maintain her current weight.
That's over 300 calories below the standard 2,000-calorie reference found on food labels.
Now imagine that her lifestyle changes. Perhaps she starts walking more, cycling to work or exercising regularly. Her daily energy expenditure would likely increase, and so would her maintenance calorie needs.
The important thing isn't the precise number. It's understanding why different people can need different amounts of energy, and why your own needs can change over time.
The Fine Print: Maintaining the Balance
There's a vital detail to keep in mind about the numbers generated by these formulas: they estimate your maintenance calories.
Your estimated TDEE gives you a starting point for understanding how much energy you need to maintain your current weight and activity levels.
For example, if your calculated TDEE is 2,400 calories, eating around that amount consistently would generally be expected to keep your weight relatively stable over time.
If your goals change, this maintenance estimate becomes your starting point:
- To lose weight: Weight loss generally requires a sustained calorie deficit, meaning that you consume less energy than your body uses.
- To gain weight: Weight gain generally requires a sustained calorie surplus, meaning that you consume more energy than your body uses.
- To maintain weight: You aim for a balance between the energy you consume and the energy you use.
But remember, your body isn't a calculator.
Your energy needs can fluctuate from day to day, and even the best formulas cannot account perfectly for differences in metabolism, body composition, movement and other individual factors.
The numbers are useful estimates, not exact measurements or guarantees.
And your daily calorie intake doesn't need to match your estimated target perfectly every single day. What matters more is the overall pattern over time.
Ditch the Averages
Nutrition labels are helpful tools for comparing food items, but the standard 2,000-calorie reference printed on them shouldn't dictate your personal diet.
Your body is not a generic statistic.
Formulas like Mifflin-St Jeor and TDEE calculations help you move beyond a one-size-fits-all approach and find a sensible starting point.
But the calculation is only the beginning. Your activity, your habits and how your body responds over time all matter.
The aim isn't to find one perfect number. It's to find a useful target that works for you.