BMI, calories, macros, calories burned, ideal weight, water, fibre and BMR — in one place.
This sits within the NHS healthy weight range for adults aged 18-64.
BMI is a useful general signal but it can mislead. It doesn't distinguish muscle from fat, doesn't show fat distribution, and uses thresholds developed for Western European populations.
Athletes or those with significant muscle mass; pregnant, postpartum or breastfeeding; over 65 or under 18; South Asian, Chinese, Black or Middle Eastern heritage (NHS uses adjusted thresholds); conditions affecting body composition (PCOS, thyroid).
If you're worried about your weight or your relationship with food, you don't have to figure it out alone. Beat, the UK's eating disorder charity, runs a free confidential helpline on 0808 801 0677.
Visit beateatingdisorders.org.uk or speak to your GP.
Uses the Mifflin-St Jeor equation — currently the most accurate formula for estimating Basal Metabolic Rate (BMR) in healthy adults. Your BMR is multiplied by your activity level to give Total Daily Energy Expenditure (TDEE).
A 500 kcal daily deficit typically produces around 0.5kg (1lb) of weight loss per week. Going below 1,200 kcal/day for women or 1,500 kcal/day for men isn't recommended without medical supervision.
Calorie calculators are estimates, not medical prescriptions. If counting calories starts to feel obsessive, controlling, or distressing, please pause and speak to someone.
The UK eating disorder charity Beat is on 0808 801 0677 — free, confidential.
Macronutrients are protein, carbohydrates and fat — the three nutrients your body needs in larger amounts. Tracking macros gives more control over body composition than calories alone.
General health: 0.8g/kg minimum. Active adults: 1.2-1.6g/kg. Muscle building: 1.6-2.2g/kg (current research consensus).
Macro tracking is useful for specific goals (building muscle, sports nutrition) but isn't necessary for general health. Most adults do fine focusing on balanced meals.
If tracking is making mealtimes stressful, that's a signal to step back.
Uses MET values (Metabolic Equivalent of Task) — a standardised measure of exercise intensity from the Compendium of Physical Activities. The formula: calories per minute = (MET × weight in kg × 3.5) / 200.
Actual calorie burn varies by fitness level, intensity, terrain and individual metabolism. Wearable tracker estimates and these calculations can differ by 20-30% — treat all numbers as ballpark.
There is no single ideal weight for any individual. This calculator gives the NHS healthy weight range for your height, adjusted slightly for frame size. Your "best" weight depends on your health, fitness, body composition and how you feel.
Wrap your thumb and middle finger around your opposite wrist. If they overlap = small frame. If they just touch = medium. If there's a gap = large.
Seeing a "target weight" can be triggering for some people, especially those with eating disorder history. If this calculator is causing distress, please close it and reach out to someone who can help.
Beat: 0808 801 0677 · beateatingdisorders.org.uk
The NHS recommends 6-8 glasses of fluid per day (around 1.5-2 litres). This calculator adjusts for body weight, activity and climate — and every result is capped at 2.5 litres of total daily water.
Simple per-kg formulas keep scaling with body weight and can suggest 4+ litres a day at higher weights. That overestimates real need, and routinely drinking very large volumes isn't safer — it can dilute blood sodium. Whatever the inputs, this calculator never recommends more than 2.5 litres.
Yes. Despite being mild diuretics, tea and coffee still contribute to daily fluid intake. Water remains the best choice — but you don't need to drink only water to stay hydrated.
Dark yellow urine, thirst, headache, fatigue, dizziness, difficulty concentrating. Pale yellow urine means you're well hydrated.
Around 20% of your daily water typically comes from food — soups, fruit, vegetables, yoghurt and sauces all contribute. The calculator deducts this automatically, so the headline figure is what you actually need to drink, not your total water need.
Pregnancy, breastfeeding, illness (fever, vomiting, diarrhoea), and intense or prolonged exercise all increase fluid needs. Speak to your GP or midwife for specific guidance.
Sip little and often from waking until early evening — roughly a small glass (150-200ml) every 45-60 minutes — rather than a few large drinks. Never try to catch up by drinking a big share of your target within a single hour: the body can only absorb so much at once, and drinking excessive amounts quickly can dangerously dilute blood sodium (hyponatraemia).
Try not to drink in the 30 minutes before a meal, with the meal itself, or for 30-60 minutes afterwards. Drinking with food fills the stomach, dilutes digestion and — after stomach surgery — can push food through too quickly. Plan your drinks between meals instead.
Follow your surgical team's fluid target, not a calculator. Most bariatric teams aim for roughly 1.5-2 litres a day taken as small, frequent sips — a reduced stomach can't hold large volumes. Avoid drinking within 30-60 minutes either side of meals, skip straws and fizzy drinks in the early months, and treat any figure above as an upper guide only.
Roughly how much of each do you eat on an average day? These are rough estimates — real fibre varies by food and portion.
About 11g below the NHS target of 30g a day — roughly where most UK adults sit. A serving of beans or pulses (~6g) and an extra wholegrain (~3.5g) would close most of the gap. Build up gradually.
This is a rough estimate, not a food diary — actual fibre depends on the specific foods and portions you eat. The NHS recommends 30g of fibre a day for adults, and most UK adults manage only around 20g. Whole foods — fruit, veg, wholegrains, beans, nuts and seeds — are the best sources.
Different fibres feed different gut bacteria, so a mix of sources does more than loading up on one. Aim for range — several plant types across the day — rather than a single "super" food.
If you're increasing your fibre, do it slowly and drink plenty of water. Going from a low intake to a high one too fast commonly causes bloating, gas and discomfort.
If you have IBS or another gut condition, more fibre — certain types especially — can make symptoms worse for some people. Check with your GP before any big change.
Basal Metabolic Rate is the energy your body uses at complete rest — keeping your organs running, body temperature stable, cells repaired. It accounts for 60-70% of your total daily calorie burn.
BMR is calories at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by your activity level — the total calories you actually burn in a day.
Yes, slightly. Muscle burns more calories at rest than fat, so increased muscle mass raises your BMR. The effect is modest (around 13 kcal per kg of muscle per day) but compounds over time.
This calculator uses the Mifflin-St Jeor equation, currently the most accurate BMR formula for healthy adults. It accounts for sex, age, height and weight.
Estimates can be ±10% off your true BMR. Indirect calorimetry (in a clinic) is the only way to measure it precisely.