What is the NHS 7700 kcal 1 kg fat rule?

The NHS 7700 kcal rule states that 1 kg of stored body fat contains approximately 7,700 kilocalories of energy. This means that to lose 1 kg of fat, you need to create a total calorie deficit of approximately 7,700 kcal. At a daily deficit of 500 kcal, this takes approximately 15 days (about 0.5 kg per week). At a deficit of 1,000 kcal/day, it takes approximately 7.7 days (close to 1 kg per week). This is the physiological basis for all NHS weight loss timeline calculations.

What is the NHS calorie deficit recommendation?

The NHS recommends a daily calorie deficit of 500–1,000 kcal for safe weight loss of 0.5–1 kg per week. A 500 kcal deficit is the NHS standard recommendation for most adults. Deficits above 1,000 kcal/day are not recommended without medical supervision. Daily intake should not fall below 1,200 kcal for women or 1,500 kcal for men without GP oversight.

What is a free TDEE calculator?

A free TDEE calculator estimates your Total Daily Energy Expenditure — the total calories your body burns in 24 hours including exercise and activity. Our free NHS calorie calculator uses the Mifflin-St Jeor BMR formula combined with an activity multiplier to calculate your personalised TDEE. From this, it subtracts your chosen calorie deficit to give your daily calorie intake target for weight loss.

Is a 500 calorie deficit safe according to NHS guidelines?

Yes — a 500 kcal daily deficit is safe for most healthy adults and is the NHS standard recommendation. It produces approximately 0.5 kg of fat loss per week, consistent with the NHS safe rate of 0.5–1 kg/week. At this rate, the deficit is small enough to avoid significant muscle loss, nutritional deficiency, or hormonal disruption. It represents the ideal balance between meaningful fat loss and long-term sustainability.

How accurate is the NHS calorie calculator?

Our NHS calorie calculator uses the Mifflin-St Jeor formula — the most clinically validated BMR formula for healthy adults. It is generally accurate within 10–15% for most people. However, individual variation in muscle mass, metabolism, and hormonal factors means results may vary. Use your calculated intake as a starting point and adjust based on 3–4 weeks of real-world progress. Recalculate every 5 kg of weight lost.

How many calories to lose 1 kg per week UK?

To lose 1 kg per week in the UK, you need a total weekly calorie deficit of approximately 7,700 kcal — which equals a daily deficit of approximately 1,100 kcal. This is the upper limit of the NHS-recommended safe range. This deficit should be achieved through both dietary reduction and increased physical activity, not dietary restriction alone. Our NHS calorie deficit calculator gives your exact daily target based on your personal TDEE.

NHS Calorie Deficit Calculator – How Many Calories to Lose Weight UK 2026

Q: How many calories should I eat to lose weight UK?

To lose weight in the UK at the NHS-recommended safe rate of 0.5–1 kg per week, most adults should create a daily calorie deficit of 500–1,000 kcal below their TDEE (Total Daily Energy Expenditure). Our NHS calorie deficit calculator uses the Mifflin-St Jeor formula to calculate your personal TDEE and recommended daily calorie intake. NHS guidelines advise not going below 1,200 kcal/day for women or 1,500 kcal/day for men without GP supervision.

Q: What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — to power breathing, circulation, organ function, and cell repair. TDEE (Total Daily Energy Expenditure) is your total daily calorie burn including all activity. TDEE = BMR × activity multiplier (1.2 for sedentary to 1.725 for very active). Your daily calorie intake target for weight loss = TDEE minus your chosen deficit (typically 500–1,000 kcal). Our free NHS calorie calculator computes both automatically.

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Written by BMI Calculator NHS Editorial Team Nutrition & Weight Management Writers specialising in NHS calorie deficit guidance and UK weight loss standards

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Medically Reviewed NHS-Aligned Health Review Panel Reviewed against NHS Live Well calorie guidance, NICE Obesity CG43, and Mifflin-St Jeor formula validation studies · July 2026

NHS Calorie Deficit Calculator — How It Works

This free NHS calorie deficit calculator uses the Mifflin-St Jeor formula to estimate your TDEE (Total Daily Energy Expenditure) — the total calories your body burns each day — and then calculates your personalised daily calorie target for safe weight loss, maintenance, or weight gain.

The key NHS principle underpinning every calculation is the 7,700 kcal rule: one kilogram of stored body fat contains approximately 7,700 kilocalories of energy. This means that to lose 1 kg of fat, your body must burn 7,700 kcal more than you consume. At a daily deficit of 500 kcal (the NHS standard recommendation), this takes approximately 15 days — producing a consistent loss of approximately 0.5 kg per week.

Before using this tool, check your current BMI with our BMI Calculator NHS and find your target weight with our ideal weight calculator UK. Then use the NHS weight loss calculator to see how many weeks your calorie deficit will take to reach your goal.

The NHS 7700 kcal Per 1 kg Fat Rule — Explained

The NHS 7,700 kcal = 1 kg fat rule is the physiological basis for all NHS weight loss timeline calculations and calorie deficit targets. Here is exactly how it works:

NHS 7700 kcal Rule — The Maths

1 kg fat = 7,700 kcal stored energy

Daily deficit of 500 kcal × 7 days = 3,500 kcal/week = ~0.45 kg/week fat loss

Daily deficit of 1,000 kcal × 7 days = 7,000 kcal/week = ~0.9 kg/week fat loss

To lose 10 kg: need 77,000 kcal total deficit = 154 days at 500 kcal/day

Note that this 7,700 kcal figure is often cited as "exactly 7,700" but in practice varies slightly between individuals (typically 7,000–8,000 kcal/kg) due to differences in fat cell composition. The NHS and most clinical guidelines use 7,700 as the standard reference value for planning purposes.

How Many Calories to Lose Weight UK — Quick Reference

Your exact calorie target depends on your personal TDEE (calculated by the tool above). The table below shows what the NHS calorie deficit recommendation means for a typical UK adult — use it as orientation while the calculator gives your personalised figures:

Daily Deficit	Weekly Loss	Monthly Loss	NHS View
200–300 kcal/day	~0.2 kg	~0.9 kg	Gentle — sustainable
✅ 500 kcal/day	~0.5 kg	~2.2 kg	NHS standard recommendation
750 kcal/day	~0.7 kg	~3.2 kg	Acceptable with care
1,000 kcal/day	~0.9 kg	~4.3 kg	NHS upper safe limit
1,500+ kcal/day	~1.4 kg+	~6+ kg	Not recommended — GP supervision needed

📋 Key NHS Calorie Facts — 2026

🔥NHS 7700 rule: 1 kg of body fat = approximately 7,700 kcal
📉NHS calorie deficit: 500–1,000 kcal below TDEE per day
⚠️NHS minimum: 1,200 kcal/day (women); 1,500 kcal/day (men) without GP supervision
🏃NHS exercise: Split deficit between diet AND activity — not diet alone
🎯NHS safe rate: 0.5–1 kg per week = approximately 500–1,000 kcal/day deficit
📊Formula used: Mifflin-St Jeor BMR × activity multiplier = TDEE

NHS Calorie Calculator — The Mifflin-St Jeor Formula Explained

Our NHS calorie calculator uses the Mifflin-St Jeor equation — the most clinically validated BMR (Basal Metabolic Rate) formula for healthy adults, and the formula most widely used by NHS dietitians and registered nutritionists in the UK.

Why Mifflin-St Jeor?

The Mifflin-St Jeor formula was developed in 1990 and validated across multiple independent population studies. It consistently outperforms older formulas (Harris-Benedict, Katch-McArdle) in accuracy for both normal-weight and overweight adults. A systematic review of BMR prediction equations found Mifflin-St Jeor to be accurate within 10% for approximately 82% of individuals — the highest accuracy of any commonly used formula.

Mifflin-St Jeor BMR Formula

Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5

Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

TDEE = BMR × activity multiplier

Sedentary = ×1.2 · Light = ×1.375 · Moderate = ×1.55 · Active = ×1.725

Calorie target = TDEE − daily deficit (500–1,000 kcal)

Free TDEE Calculator — What Your TDEE Means

TDEE (Total Daily Energy Expenditure) is the most important number in weight management. It represents the total calories your body burns in 24 hours — accounting for everything from breathing and organ function (BMR) to deliberate exercise and everyday movement (NEAT). Your TDEE is your maintenance calorie level: eat exactly this amount and your weight stays constant; eat less and you lose weight; eat more and you gain.

Average TDEE values for UK adults in 2026 (approximate):

Sedentary women (30–40 years, 65–75 kg): approximately 1,700–1,900 kcal/day
Moderately active women: approximately 2,000–2,200 kcal/day
Sedentary men (30–40 years, 80–90 kg): approximately 2,100–2,300 kcal/day
Moderately active men: approximately 2,400–2,700 kcal/day

These are population averages — your personal TDEE from the NHS calorie deficit calculator above will give a more accurate figure. Recalculate every 5 kg of weight lost, as your TDEE decreases as you become lighter.

How Many Calories to Lose Weight UK — Practical Example

Here is how the NHS calorie deficit calculation works in practice for a real UK adult:

📋 Example: Sarah, 38 years old, 172 cm, 85 kg, moderately active.
BMR (Mifflin-St Jeor) = (10 × 85) + (6.25 × 172) − (5 × 38) − 161 = 850 + 1,075 − 190 − 161 = 1,574 kcal/day at rest
TDEE = 1,574 × 1.55 (moderately active) = 2,440 kcal/day
NHS calorie deficit (500 kcal): 2,440 − 500 = 1,940 kcal/day target
Expected loss at this intake: approximately 0.45–0.5 kg per week
To reach healthy BMI (24.9 = 73.7 kg): approximately 11.3 kg to lose = 23–25 weeks at 500 kcal deficit

Use the NHS weight loss calculator to generate your personalised timeline from your goal weight. To see your healthy weight range for your height, use our ideal weight calculator UK. To check your starting BMI, use our visual BMI calculator.

How to Create Your NHS Calorie Deficit — Practical Guide

Knowing your calorie target is the first step. The second step is creating the deficit in practice. The NHS recommends splitting the deficit between dietary reduction and increased physical activity — not achieving it entirely through food restriction, which makes the approach far less sustainable.

Step 1 — Reduce Dietary Calories (250–500 kcal from food)

Reduce portion sizes by 20–25% at main meals — this alone creates a 200–400 kcal daily reduction for most people
Eliminate liquid calories — sugary drinks, fruit juice, alcohol, and high-calorie coffees can add 300–600 kcal daily without providing satiety
Swap ultra-processed foods for whole food alternatives — this reduces calorie density dramatically while increasing fibre and satiety
Prioritise protein (1.2–1.6 g/kg body weight) — the most satiating macronutrient, critical for preserving muscle mass during a deficit
Follow NHS Eatwell Guide proportions — half plate vegetables/fruit, quarter wholegrains, quarter lean protein

Step 2 — Increase Activity (250–500 kcal from movement)

NHS target: 150 minutes of moderate aerobic activity per week (brisk walking, cycling, swimming, dancing)
Walking 8,000–10,000 steps daily burns approximately 250–400 kcal — a significant contribution to the daily deficit
Resistance training 2–3 times/week preserves lean muscle mass and maintains your metabolic rate as you lose weight
NEAT (Non-Exercise Activity Thermogenesis) — taking stairs, standing more, walking short distances — can burn 200–400 kcal extra daily

Step 3 — Track, Review, Adjust

Weigh yourself once weekly at the same time of day — focus on the 4-week trend, not daily fluctuations
If weight loss stalls for 3–4 weeks despite adherence, reduce intake by a further 100–150 kcal
Recalculate your TDEE after every 5 kg lost — your maintenance calories decrease as you become lighter, so the deficit needs adjusting
Track BMI category progress with our BMI progress tracker

⚠️ NHS Minimum Intake Warning: Never eat below 1,200 kcal/day (women) or 1,500 kcal/day (men) without direct GP supervision. At these calorie levels it becomes impossible to meet all essential micronutrient requirements from food alone. Very Low Calorie Diets (under 800 kcal/day) are a clinical intervention requiring medical oversight — they are not appropriate for self-directed NHS weight loss.

✅ Your Complete NHS Weight Management Toolkit: NHS Calorie Deficit Calculator (this page) → NHS Weight Loss Calculator → Ideal Weight Calculator UK → BMI Progress Tracker. All free, all NHS-aligned.

Sources & References

NHS Live Well — Calorie Checker and Weight Loss: nhs.uk
NICE Guideline CG43 — Obesity: Identification, Assessment and Management (2023): nice.org.uk
Mifflin MD, St Jeor ST et al. — A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.
Hall KD et al. — Energy balance and its components: implications for body weight regulation. American Journal of Clinical Nutrition, 2012.
NHS Eatwell Guide: NHS Eatwell Guide

⚠️ Medical Disclaimer: This NHS calorie deficit calculator is for informational and educational purposes only. TDEE calculations are estimates that may vary ±10–15% from actual values due to individual metabolic differences. This tool is not suitable for pregnant or breastfeeding women, those with eating disorders, or adults with serious underlying health conditions. BMI Calculator NHS is not affiliated with NHS England, NICE, or any government body. Always consult your GP or a registered dietitian before starting a calorie-restricted programme. See our Disclaimer, Privacy Policy, and Terms of Service.

Frequently Asked Questions — NHS Calorie Deficit Calculator

The number of calories you need to lose weight depends on your TDEE (Total Daily Energy Expenditure), calculated from your height, weight, age, sex, and activity level. Use our NHS calorie deficit calculator above for a personalised answer. As a general guide: most UK adults lose weight safely at 1,400–2,000 kcal/day — a 500–1,000 kcal reduction from their TDEE. NHS guidelines say not to go below 1,200 kcal (women) or 1,500 kcal (men) without GP supervision.

The NHS 7,700 kcal rule states that 1 kg of stored body fat contains approximately 7,700 kilocalories. To lose 1 kg of fat, you need to create a total calorie deficit of 7,700 kcal. At a daily NHS calorie deficit of 500 kcal, this takes approximately 15 days (0.5 kg/week). At 1,000 kcal/day deficit, approximately 7.7 days (~1 kg/week). This rule is the physiological basis for all NHS weight loss timelines — see our NHS weight loss calculator for your personalised timeline.

The NHS calorie deficit recommendation is 500–1,000 kcal below your TDEE per day for safe weight loss. A 500 kcal/day deficit produces approximately 0.5 kg/week; a 1,000 kcal/day deficit produces approximately 1 kg/week. These represent the lower and upper boundaries of the NHS safe rate. The NHS recommends splitting the deficit between dietary reduction and physical activity — not achieving it through food restriction alone.

A free TDEE calculator estimates your Total Daily Energy Expenditure — the total calories your body burns in 24 hours including all activity. Our NHS calorie calculator above does exactly this, using the Mifflin-St Jeor BMR formula multiplied by your activity level to give your personal TDEE. It then shows your recommended daily calorie intake for weight loss, maintenance, or weight gain. TDEE decreases as you lose weight — recalculate every 5 kg lost.

Yes — a 500 kcal daily NHS calorie deficit is safe for most healthy adults and is the NHS standard recommendation. It produces approximately 0.5 kg of fat loss per week — the lower end of the NHS safe rate. At this rate, the deficit is small enough to avoid significant muscle loss, nutritional deficiency, or hormonal disruption. It represents the ideal balance between meaningful fat loss and long-term sustainability. See our safe rate of weight loss per week guide for the evidence.

Our NHS calorie calculator uses the Mifflin-St Jeor formula — the most clinically validated BMR formula for healthy adults, accurate within 10% for approximately 82% of people in validation studies. Individual variation in muscle mass, gut microbiome, and hormonal factors means your real TDEE may differ from the calculation. Use the result as a starting point and adjust based on 3–4 weeks of real-world progress. Recalculate after every 5 kg lost.

To lose 1 kg per week UK, you need a total weekly calorie deficit of approximately 7,700 kcal (the NHS 7700 kcal rule) — which equals a daily deficit of approximately 1,100 kcal. This is near the upper limit of the NHS safe range. It should be achieved through both eating less and exercising more. For most adults, this means aiming for approximately 1,200–1,800 kcal/day depending on TDEE. Use our NHS calorie deficit calculator above for your exact personal target.

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — for breathing, circulation, organ function, and cell repair. It accounts for approximately 60–70% of total calorie burn. TDEE (Total Daily Energy Expenditure) is your total 24-hour calorie burn including all activity. TDEE = BMR × activity multiplier. Your daily calorie target for weight loss = TDEE minus your chosen deficit. Our free NHS calorie calculator computes both automatically from your details.