Calorie Calculator

How Daily Calorie Needs Are Estimated

A calorie calculator estimates how many kilocalories (kcal) your body burns in 24 hours. It works in two stages. First it estimates your Basal Metabolic Rate (BMR) — the energy your body uses at complete rest to keep your heart, brain, kidneys and other organs running. Then it multiplies that by an activity factor (PAL) to give your Total Daily Energy Expenditure (TDEE), which is the headline number most people are looking for.

In the UK, the NHS and the British Dietetic Association (BDA) reference two anchor figures from the NHS Eatwell Guide: roughly 2,000 kcal per day for women and 2,500 kcal per day for men. Those are general population averages for a moderately active adult — they are not personalised targets, and the NHS is explicit that they should be used as a rough reference, not as a goal. Mandatory calorie labelling in large UK food businesses (250+ employees), introduced in April 2022, uses the same 2,000 kcal reference on menus and packaging.

The number this calculator gives you is almost always more useful than the 2,000/2,500 reference, because it accounts for your actual age, sex, height, weight and activity level. A 5'2" sedentary 60-year-old woman and a 6'1" active 25-year-old woman both get "2,000 kcal" on the back of a sandwich, but their real maintenance figures can differ by 700-900 kcal a day.

Most American calorie calculators online still use the older Harris-Benedict equation (1919, revised 1984). The NHS, the BDA and most modern UK clinical practice use Mifflin-St Jeor (1990) instead, because a 2005 systematic review in the Journal of the American Dietetic Association found it predicted resting energy expenditure within 10% for the largest share of adults. Harris-Benedict tends to overestimate by 5-15%, particularly in people with lower muscle mass. That is the editorial choice this calculator makes — Mifflin-St Jeor first, in line with NHS practice — and it is the main reason your number here may read 100-300 kcal lower than on a US site.

For context on how the UK actually eats: the Public Health England / UKHSA National Diet and Nutrition Survey (NDNS) consistently shows average adult intake running close to 1,900-2,100 kcal/day for men and 1,600-1,800 kcal/day for women — under-reporting in food diaries is well documented, and true intake is widely accepted to be higher. The Sugar Reduction and Calorie Reduction programmes (2017-2022) attempted to cut calorie density across savoury convenience foods; results have been mixed. None of that changes your personal number, but it explains why a result of 2,300 kcal can feel "a lot" when survey averages look lower.

How to Calculate Your Daily Calorie Requirement

Enter your age, sex, height in centimetres and weight in kilograms. Pick the activity level that matches a typical week (not your best week). The calculator returns your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE) and a sensible deficit/surplus range based on BDA guidance.

1. Enter your age in years. Use whole years, not months.
2. Select your sex (the formula needs biological sex because BMR differs by ~150-200 kcal at the same height/weight).
3. Enter your height in centimetres. If you only know feet/inches, multiply inches by 2.54.
4. Enter your weight in kilograms, ideally first thing in the morning after the toilet. If you weigh in stones, 1 st = 6.35 kg.
5. Choose your activity level honestly — this is where most people inflate their TDEE by 300-600 kcal.
6. Click Calculate. You will see your BMR, your TDEE, and recommended ranges for cutting and gaining.
7. Subtract roughly 500 kcal/day from TDEE for steady weight loss, or add 250-500 kcal/day for a lean gain. The BDA cap is around 500-600 kcal/day below maintenance for sustainable loss.
8. Recheck the number after every 3-5 kg of weight change, or sooner if your activity pattern shifts.

Mifflin-St Jeor vs Harris-Benedict: Which Equation Is More Accurate?

The formula used: Mifflin-St Jeor: BMR (men) = 10W + 6.25H - 5A + 5. BMR (women) = 10W + 6.25H - 5A - 161. TDEE = BMR x Activity Factor (PAL 1.2 to 1.9)

Calorie Estimates for Sedentary, Active, and Athletic Lifestyles

A 40-year-old man, 180 cm, 85 kg, moderately active: BMR = (10 x 85) + (6.25 x 180) - (5 x 40) + 5 = 1,780 kcal. TDEE = 1,780 x 1.55 = 2,759 kcal. A 500 kcal/day deficit puts the daily target at roughly 2,259 kcal for around 0.5 kg weight loss per week.

When to Recalculate Your Calorie Target

Use this calculator at the start of any deliberate change in eating or training, and at regular intervals after that. Body weight is the single biggest input into BMR, so the number drifts as you do.

Recalculate after every 3-5 kg of weight change. A 5 kg loss alone reduces BMR by ~50 kcal/day in the formula, and TDEE by 60-95 kcal/day depending on activity level. Combined with adaptive thermogenesis (the metabolic slowdown that accompanies sustained dieting), the real shift is often larger — which is why people stall after the first 4-6 weeks of a deficit.

Recalculate when activity changes. Starting a new job, breaking a long bone, returning from injury, taking on a marathon block, or moving from a desk role to a trade job all change the multiplier — sometimes by a full PAL band.

Pregnancy is a special case. NHS guidance is that no extra calories are needed in the first or second trimester for women starting pregnancy at a healthy weight. About 200 kcal/day extra is recommended in the third trimester only. Exclusively breastfeeding mothers are typically advised to add 330-400 kcal/day. This calculator is not designed for pregnancy or breastfeeding — your midwife or a registered dietitian (RD) is the right source.

Older adults (65+) should be cautious. NHS and BDA guidance both warn against routine calorie restriction in later life because of the risk of sarcopenia (age-related muscle loss), micronutrient deficiency and frailty. If you are over 65 and considering weight loss, speak to your GP first — Tier 2 and Tier 3 NHS weight management services exist for clinically indicated cases.

Do not use this calculator as a target if you are pregnant or breastfeeding, under 18, have a BMI below 18.5 or above 40, are recovering from an eating disorder, or have a medical condition affecting metabolism (thyroid disease, Cushing's syndrome, chronic kidney disease, certain cancers). In all of those cases speak to your GP or a HCPC-registered dietitian.

BMR, TDEE, and Activity Multipliers Explained

Mifflin-St Jeor vs Harris-Benedict vs WHO Equations Compared

Tips for Setting a Realistic Calorie Goal

• Cap the deficit at ~500-600 kcal/day below maintenance. The BDA considers 0.5-1 kg of weight loss per week the safe sustainable range — anything faster is usually water and lean tissue.
• Do not eat below ~1,200 kcal (women) or ~1,500 kcal (men) without GP or registered dietitian supervision. Below those floors it is hard to hit micronutrient targets even on a well-planned diet.
• Anchor the diet to the NHS Eatwell Guide proportions: roughly a third fruit/veg, a third starchy carbs (preferably wholegrain), with protein, dairy/alternatives and small amounts of unsaturated fat making up the rest. The calorie number is the budget; the Eatwell Guide is how to spend it.
• Hit 1.6-2.2 g of protein per kg of body weight per day during a deficit to preserve muscle. For an 80 kg adult that is 130-175 g/day.
• Weigh yourself once or twice a week first thing in the morning, after the toilet, before food or drink. Track the weekly average rather than reacting to single readings — water, glycogen and bowel content can shift body weight by 1-2 kg overnight.
• Use a digital kitchen scale for the first 2-3 weeks of a deficit. Eyeballed portions of pasta, rice, cereal and oils are the largest single source of calorie under-counting.
• Eat back at most 50-75% of fitness-tracker exercise calories — UK consumer trackers consistently overestimate burn by 20-40%, particularly for cycling and strength training.
• Recheck your TDEE every 3-5 kg of weight change. A 90 kg adult dropping to 80 kg loses roughly 100 kcal/day from BMR alone, before adaptive thermogenesis.
• If you have a medical condition (type 2 diabetes, hypertension, PCOS, hypothyroidism, IBD), discuss any calorie target with your GP or a HCPC-registered dietitian before starting.

Calorie Counting Mistakes That Stall Progress

• Picking 'moderately active' or 'very active' for a job that involves sitting most of the day and a couple of gym sessions a week. The honest answer for most UK office workers who train 2-4 times is 'lightly active' (1.375), not moderately active (1.55) — the gap is 250-400 kcal/day.
• Treating the 2,000 kcal / 2,500 kcal Eatwell Guide reference as a personal target. Those are population averages used for food labelling, not individual goals. The NHS itself flags this on its Eatwell Guide page.
• Trusting the 'calories burned' figure on a treadmill, smartwatch or spin bike at face value. Independent testing (including Stanford 2017) puts consumer-device error at 20-40% high for most activities.
• Forgetting liquid calories: a flat white (~120 kcal), a 500 ml orange juice (~225 kcal), a pint of 5% lager (~215 kcal), an oat-milk latte (~200 kcal). Five liquid 'extras' a day is comfortably 800-1,000 kcal that often goes untracked.
• Logging the cooked weight of pasta and rice as if it were the dry weight. 75 g of dry pasta becomes ~210 g cooked — logging 75 g of the cooked plate under-counts by roughly 200 kcal.
• Using oil as if it were calorie-free. A tablespoon of olive oil is ~120 kcal. Two tablespoons in a roasting tin and another in a salad dressing is 360 kcal before any food is added.
• Setting the same deficit target for months without recalculating. After 5-10 kg of loss, the original deficit may now be near zero.
• Going below 1,200 kcal (women) / 1,500 kcal (men) to 'speed things up'. Outside of specialist NHS Tier 3 programmes, very low-calorie intakes are not recommended by the BDA and routinely backfire through bingeing and lean-tissue loss.
• Restricting calories during pregnancy, breastfeeding, or active recovery from an eating disorder. None of those are appropriate uses of a TDEE calculator — speak to your midwife, GP or specialist team.
• Assuming the calculator is wrong because the scale is not moving in week one. Sodium, training-induced glycogen storage and menstrual-cycle water shifts can mask 1-2 kg of fat loss for up to 3 weeks. Use a 4-week trend, not a 4-day one.