TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including your basal metabolic rate, physical activity, and the energy used to digest food. It's the key number for weight management — eat below your TDEE to lose weight, at your TDEE to maintain, or above to gain.

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive. This includes breathing, circulation, and cell production. BMR typically accounts for 60-75% of your total daily calorie burn. You should never eat below your BMR for extended periods.

TDEE & BMR Calculator UK: How Many Calories Do You Need? (2026)

Quick Answer: Your TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns per day, including exercise. Your BMR (Basal Metabolic Rate) is what you burn at rest. To lose weight, eat below your TDEE; to gain, eat above it. NutraSafe's calorie counter helps you track your actual intake against your TDEE target, with an AI coach that adjusts recommendations based on your activity level and progress.

Understanding TDEE and BMR

To manage your weight effectively, you need to understand how many calories your body actually needs. Two key numbers help with this: TDEE and BMR.

What is TDEE?

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day. It includes everything: your resting metabolism, physical activity, digestion, and even fidgeting. This is the magic number for weight management:

Eat below your TDEE = weight loss (calorie deficit)
Eat at your TDEE = weight maintenance
Eat above your TDEE = weight gain (muscle or fat)

What is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest - just to keep you alive. This includes breathing, blood circulation, cell production, and brain function. BMR typically accounts for 60-75% of your total daily calorie burn.

Important: You should never eat below your BMR for extended periods. Doing so can lead to nutrient deficiencies, muscle loss, metabolic slowdown, and other health issues.

The Mifflin-St Jeor Equation (Most Accurate)

Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5 Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161

TDEE = BMR x Activity Multiplier (1.2 to 1.9)

How Much of a Deficit for Weight Loss?

A calorie deficit of 500 calories per day typically results in losing about 0.5kg (1lb) per week - this is considered a healthy, sustainable rate. Going too aggressive (over 750 calorie deficit) can lead to muscle loss, fatigue, and is harder to maintain long-term.

For best results, combine a moderate calorie deficit with adequate protein intake (1.6-2.2g per kg of body weight) and resistance training to preserve muscle mass while losing fat.

Activity Level Guide

Sedentary (1.2): Office job, little to no exercise
Lightly Active (1.375): Light exercise 1-3 days per week
Moderately Active (1.55): Moderate exercise 3-5 days per week
Very Active (1.725): Hard exercise 6-7 days per week
Extremely Active (1.9): Very hard exercise, physical job, or training twice daily

Most people overestimate their activity level. If in doubt, choose one level lower than you think and adjust based on real-world results.

Worked Example: TDEE for an 85kg Man

Here is a typical TDEE calculation for an 85kg man, aged 35, height 178cm (5'10"), who exercises 3-4 times per week (moderately active):

Step 1 — BMR (Mifflin-St Jeor):

BMR = (10 × 85) + (6.25 × 178) − (5 × 35) − 5 = 1,788 kcal/day

Step 2 — Multiply by activity factor (1.55):

TDEE = 1,788 × 1.55 = 2,771 kcal/day

Step 3 — Calorie targets:

Maintain weight: ~2,770 kcal/day
Lose 0.5kg/week: ~2,270 kcal/day (500 kcal deficit)
Lose 1kg/week: ~1,770 kcal/day (1,000 kcal deficit — aggressive, consider with caution)
Gain muscle: ~3,070 kcal/day (300 kcal surplus)

This is a typical range. A sedentary 85kg man of the same age would have a TDEE closer to 2,146 kcal/day (BMR × 1.2), while a very active 85kg man could be around 3,084 kcal/day (BMR × 1.725). Use the calculator above to get your personalised figure.

TDEE Calculator FAQ

How accurate is this TDEE calculator?

This calculator uses the Mifflin-St Jeor equation, which research shows is the most accurate formula for estimating metabolic rate for most people. However, all calculators provide estimates - your actual TDEE can vary based on genetics, muscle mass, hormones, and metabolic adaptations. Use the result as a starting point and adjust based on your real-world results over 2-3 weeks.

Why isn't my weight changing if I'm eating at a deficit?

Several factors could be at play: 1) You may be underestimating how much you're eating - try weighing food for more accuracy. 2) Water retention can mask fat loss for days or weeks. 3) Your TDEE may be lower than calculated - try reducing by another 100-200 calories. 4) Weekend eating may be undoing weekday progress. Give it 3-4 weeks of consistent tracking before adjusting.

Should I eat back exercise calories?

Exercise calorie estimates from fitness trackers are often 30-50% too high. If you're trying to lose weight, it's generally better to not eat back exercise calories, or at most eat back half. The activity multiplier in this calculator already accounts for regular exercise, so additional "eating back" can slow progress.

Is it safe to eat below my BMR?

Eating below your BMR for extended periods is not recommended. It can lead to nutrient deficiencies, muscle loss, hormonal disruption, and metabolic slowdown. Very low-calorie diets (under 1,200 for women, 1,500 for men) should only be followed under medical supervision. A moderate deficit from your TDEE is more sustainable and effective long-term.

TDEE & BMR Calculator

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