Nutrition Calculators & Tools
Free, accurate tools to turn nutrition advice into your own numbers. No sign-up, no spreadsheets — just enter your details and get a clear answer you can act on today. Every calculator is built on the same peer-reviewed formulas dietitians use, and each links to a plain-English guide so you understand what the number means.
Find out how many calories you burn in a day and exactly how many to eat to lose, maintain, or gain weight. Uses the Mifflin-St Jeor equation and gives you five clear goal targets.
Open calculator →Get your personal daily protein target in grams, based on your weight, activity, and goal — plus a simple per-meal breakdown so it is easy to hit. Grounded in the peer-reviewed 0.8–2.2 g/kg range.
Open calculator →Work out how much water you should drink a day based on your body weight and activity, with adjustments for exercise and hot weather. Answers in both litres and cups.
Open calculator →Turn your daily calories into gram targets for protein, carbohydrate and fat. Choose a goal-based split built on the government Acceptable Macronutrient Distribution Ranges, or set your own.
Open calculator →Prefer to read first?
Each tool is paired with a plain-English guide that explains the reasoning behind the numbers, so you can use them with confidence rather than blindly.
All calculators provide estimates for general information and education. They are not a substitute for personalised advice from a qualified dietitian or doctor, especially if you have a medical condition.
Which calculator should you use?
Each tool on this page answers a different question, and using them together gives you a complete picture of how much energy your body needs and how to divide that energy across protein, carbohydrate and fat. If you are just getting started, work from the top down: estimate your calories first, then set your protein target, then decide how the remaining calories are split, and finally check that your fluid intake keeps pace with your activity. None of these numbers are fixed rules; they are evidence-based starting points that you adjust as you see real-world results over two to four weeks.
Calorie Calculator
The Calorie Calculator estimates your total daily energy expenditure by combining your basal metabolic rate with an activity multiplier. Basal metabolic rate is the energy your body burns at complete rest to run essential functions such as breathing, circulation and cell repair, and for most adults it accounts for the large majority of daily calorie use. Use this tool when you want a realistic maintenance number to build a plan around. If your goal is fat loss, a modest deficit of roughly ten to twenty percent below maintenance is usually sustainable; if you are trying to gain lean mass, a small surplus paired with resistance training works better than a large one. Re-check the number whenever your weight changes noticeably or your training load shifts, because energy needs move with body size and activity.
Protein Calculator
The Protein Calculator turns your body weight and goals into a daily protein target in grams. Protein supports muscle repair, keeps you fuller between meals, and has the highest thermic effect of the three macronutrients, meaning your body spends more energy digesting it. Most healthy, active adults do well between roughly 1.6 and 2.2 grams of protein per kilogram of body weight, with the higher end useful when you are training hard or eating in a calorie deficit and want to protect muscle. Spreading protein across three or four meals, rather than loading it all into dinner, helps you hit the target and supports muscle protein synthesis throughout the day.
Macro Calculator
The Macro Calculator takes your calorie and protein numbers and splits the rest of your energy between carbohydrate and fat. Carbohydrate is your body's most efficient fuel for higher-intensity exercise, while dietary fat is essential for hormone production and the absorption of fat-soluble vitamins. There is no single perfect ratio: endurance athletes often benefit from more carbohydrate, while some people feel steadier on a moderate-carbohydrate plan. Because protein and carbohydrate each provide four calories per gram and fat provides nine, small changes in the split can shift your totals quickly, which is why converting every percentage into grams — as this calculator does — makes a plan far easier to follow in a real kitchen.
Water Intake Calculator
The Water Intake Calculator estimates a sensible daily fluid target based on your body weight and activity level. Hydration affects energy, concentration, temperature regulation and exercise performance, and needs rise with heat, altitude and sweat losses during training. Treat the result as a baseline rather than a hard quota: the colour of your urine and your thirst are useful day-to-day signals, and foods with high water content such as fruit and vegetables count toward your total. On heavy training days, add fluid to match what you lose, and remember that electrolytes matter alongside plain water when sessions are long or intense.
How to get the most from these tools
Calculators give you a confident starting point, but your own data is the real feedback loop. Pick your numbers, follow them consistently for two to four weeks, track weight and how you feel, then adjust in small steps rather than overhauling everything at once. If progress stalls, change one variable — usually calories or activity — and give it time before changing another. For the reasoning behind every number here, read our guides on calorie counting, protein intake, macronutrients and hydration, which explain the science these tools are built on.