How to Calculate Your TDEE (And Why It Beats Generic Calorie Targets)
The 2,000-calorie target on every food label was designed for an average adult that probably isn't you. Here's how to calculate the number that actually matches your body.
By Krishna Chaitanya, Software Engineer
Sarah has been eating 2,000 calories a day for three months. She got the number from the back of a cereal box. She's been precise about it: logging meals, weighing portions, skipping the odd biscuit. The number on the scales hasn't budged. Not down, not meaningfully up. Just stuck.
The problem isn't Sarah's discipline. The problem is the number. That 2,000-calorie figure was never hers to begin with. It belongs to a statistical construct: a reference adult used by food labelling regulators. That person doesn't exist, and they certainly aren't Sarah, 34 years old, 5'4", runs three times a week. The calories she actually needs and the calories on the label are two different things entirely.
Why Generic Calorie Targets Fail
The 2,000 kcal/day figure on UK food labels is a reference value set by the European Food Safety Authority to standardise nutritional information. It's not a prescription. It's not personalised. It bears no relationship to your height, weight, age, sex, or how active you are.
The range of actual calorie needs across adults is wide. Someone who runs 25 miles a week, lifts weights, and commutes by bicycle may need 3,000+ kcal just to maintain their current weight. Someone who works from home, drives everywhere, and doesn't exercise may need 1,600 kcal. Giving both people the same target and expecting results is like giving everyone the same shoe size and wondering why they can't walk properly.
Eating at the wrong level doesn't just slow progress. It can actively work against you. Eat too little and your body down-regulates non-essential energy expenditure, you lose muscle mass, and adherence collapses. Eat too much and the surplus gets stored. My view is that anyone serious about managing their weight should calculate their own number before they start counting anything.
BMR, TDEE, and the Mifflin-St Jeor Formula
Understanding two terms makes everything else click.
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest: lying still, not digesting food, just keeping your heart beating, your lungs breathing, and your organs functioning. It accounts for roughly 60-70% of total daily energy expenditure for most people.
TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor. It represents all the calories you burn across a full day: rest, movement, exercise, digestion, everything.
To get from one to the other, you need a reliable formula for BMR. The most validated option is the Mifflin-St Jeor equation, developed by Mifflin MD, St Jeor ST et al. and published in 1990 in the Journal of the American Dietetic Association (90(3), 450-457). It consistently outperforms older equations like Harris-Benedict for healthy adults.
The Mifflin-St Jeor formula:
For men:
BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
For women:
BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
Once you have your BMR, multiply it by your activity level:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1-3 days/week | 1.375 |
| Moderately active | Moderate exercise 3-5 days/week | 1.55 |
| Active | Hard exercise 6-7 days/week | 1.725 |
| Very active | Physical job + hard daily exercise | 1.9 |
The result is your TDEE: the calories you need to maintain your current weight. Adjust up or down from there for gain or loss.
How the TDEE Calculator Does This in 30 Seconds
Working through the formula manually is useful once. After that, it gets tedious, especially when you're recalculating after weight changes or adjusting for a new training block.
The TDEE Calculator takes your age, sex, height, weight, and activity level and returns three things instantly: your BMR, your TDEE, and calorie targets for cutting (losing weight), maintenance, and bulking (gaining muscle). Height and weight accept both metric and imperial inputs. The cut target applies a 500 kcal daily deficit; the bulk target adds a 300 kcal surplus. No arithmetic required.
If you've never calculated your personal calorie needs before, start here. Even if you've been tracking for months, running the calculation now might explain why things have stalled.
Worked Example: 32-Year-Old Woman, Moderately Active
Take a 32-year-old woman: 65kg, 168cm tall, works at a desk but goes to the gym three to four times a week. Moderately active.
Step 1: Calculate BMR using Mifflin-St Jeor (women's formula):
BMR = (10 x 65) + (6.25 x 168) - (5 x 32) - 161
BMR = 650 + 1,050 - 160 - 161
BMR = 1,379 kcal
Step 2: Multiply by activity factor (moderate = 1.55):
TDEE = 1,379 x 1.55
TDEE = 2,137 kcal/day
Step 3: Set a calorie target:
- To lose weight: 2,137 - 500 = 1,637 kcal/day
- To maintain weight: 2,137 kcal/day
- To build muscle: 2,137 + 300 = 2,437 kcal/day
That 1,637 kcal/day weight loss target is meaningfully different from 1,200 kcal crash diets and meaningfully different from the 2,000 kcal label default. It's a number that fits her body.
What to Do With Your TDEE
For weight loss, eat at a 400-500 kcal daily deficit. At 500 kcal below TDEE, you create a 3,500 kcal weekly deficit, roughly 0.5kg of fat per week. This rate is sustainable, preserves muscle mass better than aggressive cuts, and is consistent with UK dietetic guidance.
For muscle gain, eat at a 250-350 kcal surplus above TDEE. Larger surpluses don't produce faster muscle growth. They mostly produce faster fat gain.
For maintenance, eat at TDEE. Useful if you're happy with your current body composition and want to stop guessing.
One habit that matters: recalculate regularly. As your weight changes, your BMR changes. After losing 5kg, your TDEE will be lower than when you started. If you keep eating the same amount, your deficit shrinks without you noticing. That's the most common reason for plateaus, and it's entirely fixable.
Once you know your TDEE, the next step is splitting those calories into protein, fat, and carbohydrates. The Macro Calculator handles that based on your goal.
Common Mistakes to Avoid
Overestimating your activity level. This is the most frequent error. Most people who exercise 3-4 times a week but otherwise sit at a desk all day are moderately active at best. Choosing a higher multiplier inflates your TDEE by 200-400 kcal, turning a planned deficit into maintenance or even a surplus. When in doubt, choose the lower category and adjust upward based on real results.
Not recalculating as your weight changes. Your BMR is tied directly to your body mass. Every 5-6kg of weight loss reduces BMR by roughly 50-75 kcal. Over time, this adds up. Someone who lost 15kg without recalculating might now be eating at maintenance without realising it.
Setting too aggressive a deficit. Eating below 1,200 kcal/day for women or 1,500 kcal/day for men is generally not sustainable and risks nutritional deficiencies, muscle loss, and disordered eating patterns. The 500 kcal/day deficit is a ceiling for most people, not a floor. A 250-300 kcal deficit is perfectly valid and often easier to stick to over months.
For informational purposes only. Consult a registered dietitian or healthcare professional for personalised nutrition advice.
Get Your Number
The label number ignores everything that makes you different from the average. Your TDEE doesn't. Use the TDEE Calculator, enter your details, and get your BMR, TDEE, and ready-to-use targets for cutting, maintaining, or building. The whole thing takes under a minute.