Health & Fitness Calculators
Free health and fitness calculators: BMI, daily calorie needs (BMR/TDEE), body fat, ideal weight, water intake and heart-rate training zones. Quick, private and easy to use — no sign-up required.
The Health & Fitness Calculators hub collects the everyday body metrics people check most often — BMI, daily calorie needs, body fat, ideal weight, hydration, training heart-rate zones, macros and more. Whether you are starting a fitness routine, adjusting to a new diet abroad, or just curious about a number, these tools give you a quick, private reading without an app or an account. Everything runs in your browser; no data leaves your device.
Each calculator has its own page with a clear explanation of the formula, sensible default values, and answers to common questions. Enter your measurements and the result updates instantly. The results are general estimates drawn from established formulas — they are useful for tracking and planning, but they do not replace a doctor, dietitian or trainer who can account for your medical history and goals.
Calculators
- BMI CalculatorCalculate your Body Mass Index (BMI) from height and weight in metric or imperial units. See your BMI category instantly.
- BMR Calculator (Mifflin-St Jeor)Estimate your Basal Metabolic Rate (BMR) — calories burned at rest — using the Mifflin-St Jeor equation. Enter sex, age, height and weight.
- TDEE & Daily Calorie CalculatorEstimate your Total Daily Energy Expenditure (TDEE) and maintenance calories using the Mifflin-St Jeor BMR and an activity multiplier.
- Body Fat Calculator (U.S. Navy Method)Estimate body fat percentage from circumference measurements using the U.S. Navy method. Enter height, neck, waist and (for women) hip in cm.
- Ideal Weight Calculator (Devine)Estimate a reference healthy weight for your height using the Devine formula. A general guide, not a target you must hit.
- Daily Water Intake CalculatorEstimate your daily water intake from body weight and exercise. See recommended litres and approximate glasses per day.
- Heart Rate Training Zones CalculatorFind your estimated maximum heart rate and five training zones from your age. Structure cardio workouts by heart-rate zone.
- Target Heart Rate Calculator (Karvonen)Calculate your target heart rate range using the Karvonen method, which accounts for resting heart rate. Personalised training zones.
- Waist-to-Height Ratio CalculatorCalculate your waist-to-height ratio (WHtR), a simple indicator of healthy body fat distribution. Keep your waist under half your height.
- Waist-to-Hip Ratio CalculatorCalculate your waist-to-hip ratio (WHR) to assess body fat distribution and cardiovascular risk. Determine apple vs pear shape.
- Lean Body Mass CalculatorEstimate your lean body mass (everything except fat) from height and weight using the Boer formula. Useful for nutrition and training.
- Calories Burned Calculator (MET)Estimate calories burned for an activity using MET values. Enter your weight, an activity and duration to see energy expended.
- Macro Calculator (Protein / Carbs / Fat)Split your daily calories into protein, carbohydrate and fat grams. Enter your calorie target and a macro ratio.
- Protein Intake CalculatorCalculate your daily protein target in grams based on body weight and activity level. From sedentary minimums to athletic needs.
- One-Rep Max (1RM) CalculatorEstimate your one-repetition maximum (1RM) for a lift from a weight lifted for reps, using the Epley formula. Plan training loads.
- Running Pace CalculatorCalculate your running pace (min/km or min/mi) and speed from a distance and time. Plan race splits and training paces.
- VO2 Max Calculator (Cooper)Estimate your VO2 max (aerobic capacity) from the distance covered in 12 minutes using the Cooper formula. Gauge cardiovascular fitness.
- Weight Loss Target Date CalculatorEstimate how long it takes to reach a weight goal at a given daily calorie deficit. See the target date and weekly loss rate.
- Body Surface Area CalculatorCalculate your body surface area (BSA) from height and weight using the Mosteller formula. Used in some drug dosing and physiology.
- Blood Alcohol Content (BAC) CalculatorEstimate your blood alcohol content (BAC) from drinks, body weight and sex using the Widmark formula. Never use to decide if you can drive.
- Sleep Cycle & Bedtime CalculatorFind the best bedtime or wake time based on 90-minute sleep cycles. Aim to wake at the end of a cycle to feel refreshed.
How these calculators work
BMI & body composition
Body Mass Index is weight in kilograms divided by height in metres squared. It is a convenient population-level screen, but it does not distinguish muscle from fat, so very muscular people can read as “overweight” without being unhealthy. The waist-to-height and body-fat tools add context.
BMR & TDEE
Basal Metabolic Rate is the energy your body uses at complete rest. Multiplying it by an activity factor gives your Total Daily Energy Expenditure — a practical maintenance calorie target for holding, losing or gaining weight.
Training metrics
Heart-rate zones, one-rep max, running pace and VO2 max help structure and track training. They are estimates from population formulas and work best alongside perceived effort and consistent record-keeping.
Hydration & macros
Water needs rise with body size and exercise, while macro and protein targets turn a calorie goal into gram amounts for meal planning. Adjust them to your own results and preferences.
These calculators provide general health estimates and are not medical advice. Results depend on the accuracy of the values you enter and on individual factors the formulas can’t capture. Consult a qualified healthcare professional before making decisions about your diet, training or treatment.