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Health & Body

Health & Body Calculators, Guides & Tools

Use free UK-friendly tools for BMI, calories, calorie deficit, protein, macros, water intake, sleep cycles and pregnancy due date estimates.

BMI Calories Protein & macros Sleep & due dates
Start here

BMI Calculator

Calculate your body mass index using metric or imperial units, then see a broad adult BMI category with clear limitations.

kg/cm stone & pounds feet & inches Adult estimate
Open BMI calculator BMI vs body fat
Example result BMI 22.9 Example for 70kg and 175cm. BMI is a broad screening estimate, not a diagnosis or full health assessment.
Calculators

Health and body calculators

Use these tools together to move from a single number to a clearer picture of body metrics, nutrition planning, hydration, sleep and pregnancy timing.

Primary tool BMI Calculator Calculate body mass index using kg/cm or stone, pounds, feet and inches. Calories Calorie Calculator Estimate BMR, maintenance calories and broad calorie targets from age, size and activity. Weight planning Calorie Deficit Calculator Estimate target calories and rough weekly progress from a daily calorie deficit. Weight range Ideal Weight Calculator See a broad healthy BMI-based weight range and formula-based estimate. Body composition Body Fat Percentage Calculator Use tape measurements for a rough body fat estimate and compare it with BMI. Nutrition Protein Intake Calculator Estimate daily protein using body weight and goals, with a UK adult baseline. Hydration Water Intake Calculator Estimate daily fluid needs from weight, activity and warmer conditions. Macros Macro Calculator Turn a calorie target into grams of protein, carbs and fat using flexible splits. Sleep Sleep Cycle Calculator Estimate bedtimes or wake-up times using common 90-minute sleep cycles. Pregnancy Pregnancy Due Date Calculator Estimate a due date from last period or conception date, with clear caveats. Related Calorie Counter by Food Look up food calories alongside calorie, macro and protein planning tools.
How to use this hub

Choose the calculator by the question you need answered

1
Checking a body metric? Start with BMI, then compare it with body fat percentage or a broad healthy weight range if you need more context.
2
Planning calories? Use the calorie calculator first, then the calorie deficit calculator only if you want to model a cautious change.
3
Setting nutrition targets? Use protein intake and macro calculators together. Treat the outputs as planning ranges, not fixed medical targets.
4
Thinking about hydration? Use the water calculator as a general estimate, but follow professional advice if you have fluid restrictions or a health condition.
5
Planning sleep times? Use the sleep cycle calculator for rough bedtime or wake-up windows, not as a guarantee of sleep quality.
6
Estimating a due date? Use the due date calculator for a first estimate, then rely on your midwife, GP or dating scan for more accurate guidance.
Guides

Health and body guides

These supporting guides explain what the calculators can tell you, where they are useful and where they can be misleading.

Body metrics BMI vs Body Fat: Which Is More Useful? Compare BMI with body fat percentage and learn why no single number tells the whole story. Calories How Many Calories Do You Need Per Day? Understand BMR, TDEE, activity levels and maintenance calories in plain English. Weight loss What Is a Safe Calorie Deficit? Learn why a smaller, sustainable deficit is usually more useful than aggressive restriction. Protein Protein Intake for Weight Loss, Muscle and Maintenance See how protein targets can change by goal, body weight and activity level. Macros Macros Explained: Protein, Carbs and Fat Made Simple Understand macro percentages, grams and how they connect to calorie planning. Hydration How Much Water Should You Drink Per Day? Understand fluid intake, activity, weather and why one exact number does not fit everyone.
Glossary

Health and body glossary terms

Use these plain-English definitions when calculator inputs mention body, nutrition, hydration, sleep or pregnancy terms.

BMIBody mass index, a weight-to-height screening estimate. Basal metabolic rateThe estimated energy your body uses at rest. TDEETotal daily energy expenditure, including activity. Calorie deficitEating fewer calories than your estimated maintenance needs. Maintenance caloriesThe estimated calories needed to maintain weight. MacronutrientsProtein, carbohydrate and fat in the diet. ProteinA nutrient used for growth, repair and maintenance. Body fat percentageThe estimated share of body weight that is fat mass. HydrationHaving enough fluid for normal body function. Estimated due dateAn estimated pregnancy date, not a guaranteed birth date.

Use the results as a starting point, not a diagnosis

Health and body calculators can help you understand estimates, compare ranges and plan questions. They cannot replace medical advice, clinical checks or support from a qualified professional.

Start with BMI Estimate calories
Health caution

Do not use these tools for emergency symptoms, eating disorder support, pregnancy concerns, medication decisions, child growth assessment or diagnosis. Speak to a GP, midwife, dietitian or qualified clinician where appropriate.