Nutrition & Energy Calculators
Six calculators covering what your body burns and what it needs back — energy, protein, macros and hydration.
Work through them in order
These tools stack. Start with the BMR Calculator — your basal metabolic rate is what you would burn lying still for 24 hours, and it is typically 60–70% of your total. Multiply it by an activity factor and you get TDEE, from the TDEE Calculator: the energy you actually use in a normal day. Everything else is a decision about how far above or below TDEE to eat.
Calories set the direction, macros set the quality
Weight change follows the energy balance, so the Calorie Calculator is where a goal becomes a daily number. But two diets at the same calorie count can feel and perform completely differently. The Macro Calculator splits that number into protein, carbohydrate and fat, and the Protein Calculator sets a protein floor — which matters most in a deficit, where adequate protein is what preserves muscle rather than losing it alongside fat.
Estimates, not measurements
Every equation here is a population average fitted to a person. Predictive BMR formulas are typically accurate to within about 10% for most adults, which on a 2,000 kcal target is a 200 kcal band. Use the number as a starting point, then adjust based on two to three weeks of real-world results rather than trusting the formula over your own data.
Body composition changes the picture
Energy needs scale with lean mass, so the same weight can carry different requirements. Check where you sit with the BMI Calculator and the Body Fat Calculator before treating any calorie target as fixed — the leaner you are, the higher your BMR at a given bodyweight.
Hydration is the one that scales with everything else
Water need is not a fixed two litres. It rises with body mass, ambient temperature, altitude and — most of all — sweat rate during exercise, which can exceed a litre an hour in heat. The Water Intake scales a baseline from bodyweight and adds an allowance for activity, which is closer to reality than a flat daily target. Food contributes too: fruit, vegetables and soups typically supply a fifth to a third of total intake, so the number the calculator gives you is not all drinking water. Thirst is a reliable enough signal for most healthy adults at rest, but it lags behind need during long or hot sessions, which is where a planned intake beats waiting to feel thirsty.
Frequently asked questions
Why do different calculators give me different calorie targets?＋
Because they use different equations. Mifflin-St Jeor, Harris-Benedict and Katch-McArdle were each fitted to different populations, and the last uses lean mass rather than total weight. Differences of 100–200 kcal between them are normal. Pick one, use it as a starting point, and let two to three weeks of real results correct it.
How fast should I lose or gain weight?＋
A deficit or surplus of roughly 15–20% of TDEE is the usual guidance — for most adults that is around 0.5–1% of bodyweight per week. Faster loss costs more lean mass and is harder to sustain; faster gain is mostly fat. The calorie calculator lets you set the rate, so choose one you can hold for months rather than weeks.
Do macros matter if I hit my calories?＋
For weight change, calories dominate. For everything else — hunger, training performance, how much of a loss comes from fat rather than muscle — the split matters. Protein is the one worth being deliberate about, especially in a deficit; carbohydrate and fat can be traded to taste within what is left.
Can I use these if I have a medical condition?＋
Treat them as background information only. Thyroid disorders, diabetes, kidney disease, eating disorders and many medications all change energy or protein requirements in ways no general equation models. Anyone in those groups should take targets from a doctor or registered dietitian.
More health & fitness tools
Every tool listed here applies a published population formula and is indicative only. None of them can account for your individual health circumstances, and none should be used to diagnose or treat any condition. Speak to your GP or a registered dietitian for advice specific to you.
Each tool states its own assumptions and sources. Read the full disclaimer.