How many calories does it take to lose 1 kg?

Approximately 7,700 calories of deficit equals 1 kg of body fat. To lose 0.5 kg per week you need a deficit of about 550 kcal per day; to lose 1 kg per week you need roughly 1,100 kcal per day below your TDEE. Deficits larger than 1,000 kcal/day are not recommended as they accelerate muscle loss.

What is TDEE and why does it matter?

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in 24 hours — including your resting metabolism (BMR), digestion (thermic effect of food, ~10%), and all physical activity. To lose weight, eat below your TDEE. To maintain, eat at it. Always create your deficit from TDEE, never from BMR.

What is BMR and why must I stay above it?

BMR (Basal Metabolic Rate) is the minimum calories your body needs to maintain vital functions — breathing, heartbeat, organ function — at complete rest. Eating below your BMR deprives your body of energy for essential processes, causing muscle loss, hormonal disruption, and metabolic adaptation that makes future weight loss harder.

How fast is it safe to lose weight?

0.5–1 kg (1–2 lb) per week is the widely recommended safe rate for most adults. Faster loss (more than 1 kg/week) is generally water weight or muscle, not fat. A gradual pace preserves muscle mass, keeps metabolism higher, and is far more sustainable long-term. If your target date requires faster loss, consider extending the deadline.

⚖️ Weight

Weight Loss Calculator 2026

Find your daily calorie target to reach your goal weight by a chosen date. Uses the Mifflin–St Jeor BMR equation (the most accurate validated formula) and the 7,700 kcal/kg fat rule — with a built-in safety check so your target never falls below the healthy minimum.

Units

Biological Sex

The Mifflin–St Jeor formula uses different constants for men and women

Age (years)

Used in BMR formula

Height (cm)

Measure barefoot

Current Weight (kg)

Your weight today

Goal Weight (kg)

The weight you want to reach

Target Date

When do you want to reach your goal weight?

Activity Level

Be honest — most people overestimate their activity by one tier

🔬 How the Calculation Works

Step 1 — Calculate BMR (Mifflin–St Jeor 1990)

Your Basal Metabolic Rate is the calories your body burns at complete rest to keep you alive. It is calculated using the Mifflin–St Jeor equation — the most accurate validated BMR formula (American Dietetic Association, 2005):

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

Step 2 — Calculate TDEE (Total Daily Energy Expenditure)

TDEE = BMR × Activity Factor. This is your true maintenance calorie level — the amount you'd need to eat to keep your current weight stable. Activity factors: Sedentary 1.2 → Lightly Active 1.375 → Moderately Active 1.55 → Very Active 1.725 → Extra Active 1.9.

Step 3 — Calculate required daily deficit

One kilogram of body fat stores approximately 7,700 kcal. To find the daily deficit needed: (weight to lose in kg × 7,700) ÷ days until target date. This gives the calories/day you need to cut from TDEE.

Step 4 — Apply safety minimums

Your daily calorie target = TDEE − deficit. The calculator flags if the result falls below 1,200 kcal/day (women) or 1,500 kcal/day (men) — the widely cited NHS/clinical minimums below which nutritional deficiency and metabolic damage risk rises sharply. A deficit exceeding ~1,000 kcal/day also triggers a warning.

📊 Weekly Pace Guide

Weekly Pace	Daily Deficit	Assessment
0.25 kg / 0.5 lb	~275 kcal/day	✅ Very sustainable
0.5 kg / 1 lb	~550 kcal/day	✅ Recommended sweet spot
0.75 kg / 1.5 lb	~825 kcal/day	⚠️ Moderate — manageable
1 kg / 2 lb	~1,100 kcal/day	⚠️ Maximum safe — muscle loss risk
Above 1 kg/week	>1,100 kcal/day	🚨 Not recommended

Sources: NHS Weight Loss Guide; NASM Calorie Calculator guidelines; Mifflin MD et al. (1990), Am J Clin Nutr 51(2):241–7.

🥗 Tips for Sustainable Fat Loss

🥩 Prioritise protein (1.6–2.2 g/kg body weight/day)

Protein has the highest thermic effect of all macronutrients (~25% of its calories are burned digesting it) and is critical for preserving muscle mass during a calorie deficit. Losing muscle slows your BMR, making further weight loss harder. Good sources: chicken, fish, eggs, Greek yogurt, legumes, cottage cheese.

🏋️ Add resistance training 2–3 times per week

Diet alone causes you to lose roughly equal parts fat and muscle. Adding resistance training shifts this to primarily fat loss. Even 2 sessions per week of compound movements (squats, rows, push movements) is enough to preserve lean mass during a deficit.

📱 Track food accurately — weigh, don't guess

Research consistently shows people underestimate their food intake by 20–40%. Using a food scale for at least a few weeks calibrates your intuition and is the single most effective tool for staying in a deficit. Liquid calories (juices, lattes, alcohol) are commonly forgotten.

😴 Sleep 7–9 hours per night

Poor sleep raises ghrelin (hunger hormone) by up to 28% and lowers leptin (fullness hormone), making it far harder to maintain a deficit. Even one night of poor sleep increases next-day calorie intake by an average of 300 kcal. Improving sleep alone can meaningfully accelerate fat loss.

🔁 Recalculate every 4–5 kg lost

As you lose weight, your BMR and TDEE both decrease — meaning your original calorie target gradually becomes less of a deficit. Recalculate your numbers every 4–5 kg to keep making progress. This calculator is a great tool to run that recalculation.

💧 Stay well hydrated

Thirst is frequently misread as hunger. Drinking 400–500 ml of water before meals has been shown in clinical trials to reduce calorie intake at that meal. Aim for roughly 35 ml per kg of body weight per day as a starting point, more on active days.

How Does a Calorie Deficit Cause Weight Loss?

Weight loss comes down to energy balance: when you consistently consume fewer calories than you burn, your body is forced to draw on stored energy — primarily body fat. One kilogram of body fat holds approximately 7,700 kcal of stored energy. So to lose 1 kg of fat, you need to create a cumulative deficit of 7,700 kcal — equivalent to a daily deficit of about 1,100 kcal for 7 days, or a gentler 550 kcal/day over two weeks.

Why you should never eat below your BMR

Your BMR is the minimum your body needs just to stay alive. Eating below it forces your body to break down muscle tissue for fuel, slows your metabolism through hormonal adaptation, and leads to nutritional deficiencies. A slower metabolism means you need fewer calories to maintain weight in future — making long-term weight management much harder. Always create your deficit from your TDEE, keeping your intake above BMR.

Why the scale doesn't move in a straight line

Body weight fluctuates daily by 1–2 kg due to water retention, glycogen levels, sodium intake, hormonal cycles, and bowel contents. These fluctuations are not fat gain or loss. Track a weekly average (weigh daily and average the 7 days) rather than reacting to day-to-day changes. True fat loss progress is visible over 2–4 weeks of consistent tracking.

What happens after the first week (water weight)

In the first week of a calorie deficit, many people lose 2–3 kg rapidly — this is mostly water and glycogen, not fat. When you eat fewer carbohydrates, your body burns through its glycogen stores; each gram of glycogen holds ~3 g of water. This weight returns immediately if you return to normal eating. Don't be discouraged when weight loss slows after week 1 — that's when you start losing actual fat.

Frequently Asked Questions

How many calories should I eat to lose weight? +

Eat 300–500 kcal below your TDEE for safe, sustainable fat loss (0.25–0.5 kg/week). Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision — these minimums protect against nutrient deficiency and muscle loss.

How many calories to lose 1 kg of fat? +

Approximately 7,700 kcal of cumulative deficit equals 1 kg of body fat. To lose 0.5 kg/week: ~550 kcal/day deficit. To lose 1 kg/week: ~1,100 kcal/day deficit. Deficits beyond 1,000 kcal/day are not recommended as they increase muscle loss significantly.

What is TDEE and how is it calculated? +

TDEE = BMR × Activity Factor. Your BMR (using the Mifflin–St Jeor equation) × your activity multiplier gives the total calories burned per day. Sedentary: ×1.2; Lightly active: ×1.375; Moderately active: ×1.55; Very active: ×1.725; Extra active: ×1.9. Eating at TDEE = maintaining weight.

Why isn't the scale moving even though I'm eating less? +

The most common reasons: (1) Underestimating food intake — studies show people underestimate by 20–40%; weigh your food. (2) Overestimating activity — pick the activity level honestly. (3) Water retention masking fat loss — sodium, hormones, and muscle repair cause daily scale fluctuations of 1–2 kg. (4) Not enough time — check a 3–4 week trend, not day-to-day. (5) Metabolic adaptation from very low intake — consider a diet break.

Should I eat back the calories I burn during exercise? +

Depends on how you calculated TDEE. If you included your exercise in the activity factor (e.g. "Moderately Active"), do not eat back those calories — they're already in your target. If you used "Sedentary" and add workouts separately, you can eat back 50–75% of the estimated burn (not 100%, as gym machines overestimate by 15–30%).

How do I recalculate as I lose weight? +

Every 4–5 kg of weight lost, re-run this calculator with your new current weight. Your BMR and TDEE decrease as you lose weight — your original calorie target gradually becomes less of a deficit and eventually becomes maintenance. Recalculating keeps you on track and prevents a plateau.

⚕️

Health note: This calculator provides estimates based on validated formulas (Mifflin–St Jeor 1990). Individual metabolism varies by 10–15% from formula predictions. Results are a starting point — track your weight for 2–3 weeks and adjust your intake by ±100 kcal/day if progress doesn't match. Consult a doctor or registered dietitian before making major dietary changes, especially if you have a medical condition.