Health & Fitness Calculators
Work out a BMI, an estimated body fat percentage, the calories you burn at rest, or a running pace. Every calculator shows the formula it used and what the result does and does not tell you.
Which calculator do I need?
Several of these measure related things. This is the quickest way to the right one.
- Am I a healthy weight for my height?
- BMI Calculator
- What weight should I be aiming for?
- Healthy Weight
- How many calories do I burn doing nothing?
- BMR Calculator
- Is my waist measurement a risk factor?
- Waist-to-Hip Ratio
- How should I split protein, carbs and fat?
- Macro Calculator
- How much protein should I eat?
- Protein Calculator
- What is my body fat percentage?
- Body Fat Calculator
- What pace do I need for a target time?
- Pace Calculator
- What time should I go to bed?
- Sleep Calculator
Health guides
Longer explanations of the formulas behind the tools, and what they can and cannot tell you.
Understanding Health Metrics
BMI and its limits
Body Mass Index (BMI) is weight in kilograms divided by height in metres squared. It provides a useful population-level screen for healthy weight ranges but has known limitations: it cannot distinguish muscle from fat, and may underestimate health risk for people with high body fat but a BMI in the normal range.
BMR vs TDEE
Basal Metabolic Rate (BMR) is the calories your body burns at complete rest — the energy needed to breathe, circulate blood, and maintain organ function. Total Daily Energy Expenditure (TDEE) multiplies BMR by an activity factor to estimate your actual daily calorie needs. Eating below TDEE creates a calorie deficit.
Macronutrients and goals
Protein, carbohydrates, and fat are the three macronutrients. Each gram of protein or carbohydrate provides 4 calories; each gram of fat provides 9. The optimal split depends on your goals — a fat-loss phase typically increases protein to preserve muscle, while endurance athletes often prioritise carbohydrates for glycogen replenishment.
Reading body composition
Body weight alone is a poor indicator of health. Body fat percentage, lean body mass, and waist-to-hip ratio each provide insight that the scale cannot. Lean body mass — total weight minus fat — drives your calorie needs and protein requirements. Tracking LBM over time shows whether muscle is being gained or lost during a diet.
Health calculator questions
- Is BMI a good measure of health?
- It is a useful population-level screen and a poor individual verdict. BMI uses only height and weight, so it cannot tell muscle from fat — a muscular athlete and someone carrying excess fat can share a BMI. Read it alongside body fat percentage and waist measurements rather than on its own.
- What is the difference between BMR and TDEE?
- BMR is what your body burns at complete rest, keeping your organs running. TDEE is BMR plus everything else — moving, digesting, exercising. BMR is the floor; TDEE is what you actually need in a day, and it is the number to work from when planning intake.
- Which body fat formula do these use?
- The Body Fat Calculator uses the US Navy circumference method, which estimates from height and tape measurements rather than requiring a scan. It states its own margin of error: circumference methods are typically within three to four percentage points, which is fine for tracking change over time and too coarse for a single definitive number.
- Is this medical advice?
- No. These are informational tools for general fitness and planning. They cannot account for medical conditions, medication, pregnancy, or anything specific to you. Speak to a doctor or a registered dietitian before making significant changes, particularly if you have a health condition.