BMI Calculator
Calculate Body Mass Index from height and weight in metric or imperial units, see your WHO category and your healthy weight range.
Health Calculators
Estimate BMI, BMR, TDEE, macros, body fat, hydration and running pace using the published formulas clinicians and coaches use.
10 free calculators
Health & Fitness
Estimate BMI, BMR, TDEE, macros, body fat, hydration and running pace using the published formulas clinicians and coaches use.
Nine of these ten tools chain together. Understanding the order they go in is worth more than any single result, because it explains why a calorie target from one site disagrees with one from another.
The chain starts at BMR — the energy your body burns at complete rest, which is 60–70% of most people's daily total. The TDEE calculator multiplies that by an activity factor between 1.2 and 1.9 to get total daily energy expenditure. The calorie calculator turns TDEE into a goal by subtracting for a cut or adding for a bulk. The macro calculator splits that goal into protein, carbohydrate and fat grams at 4, 4 and 9 calories per gram. The protein calculator sets the protein floor independently, from body weight and training load.
The composition tools sit alongside. BMI is the quickest screen and the bluntest: it compares weight with height and knows nothing about what the weight is made of. Body fat uses the US Navy tape method to estimate composition from circumference measurements, which is where BMI's blind spot is. Ideal weight compares the Devine, Robinson, Miller and Hamwi formulas — they disagree by several kilograms at the same height, which is itself the useful finding.
The last two are practical rather than metabolic. Water intake estimates a daily fluid target from weight, exercise and climate, and running pace solves for pace, time or distance and prints a splits table for a target race.
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All 10 health calculators
BMR Calculator
Estimate basal metabolic rate — the energy your body burns at complete rest — using Mifflin-St Jeor or Harris-Benedict.
TDEE Calculator
Multiply your BMR by an activity factor to get total daily energy expenditure, the calorie number every diet plan starts from.
Calorie Calculator
Get maintenance calories plus cutting and bulking targets, with the weekly weight change each target implies.
Macro Calculator
Split a calorie target into protein, carbohydrate and fat grams using 4/4/9 energy values and a split that suits your goal.
Protein Calculator
Set a daily protein target from body weight, training load and goal, then split it sensibly across your meals.
Body Fat Calculator
Estimate body fat percentage with the US Navy tape method, and see lean mass plus the category your result falls into.
Ideal Weight Calculator
Compare the Devine, Robinson, Miller and Hamwi formulas side by side, plus the healthy BMI weight range for your height.
Water Intake Calculator
Estimate a daily fluid target from body weight, exercise minutes and climate, shown in litres, cups and fluid ounces.
Running Pace Calculator
Solve for pace, time or distance, get a splits table for your target, and see equivalent times at common race distances.
How to choose the right tool
Start where your question is. If you want to know whether your weight is in a healthy range, use BMI and then check it against body fat, because BMI misclassifies muscular people badly. If you want to change your weight, skip BMI and go straight to TDEE and calories.
Mifflin-St Jeor or Harris-Benedict? The BMR calculator offers both. Mifflin-St Jeor, published in 1990, is generally more accurate for modern populations and is the default. Harris-Benedict dates to 1919 and tends to read slightly higher. If two websites give you different calorie targets, this choice is usually why.
Be honest about the activity multiplier. It is the largest single source of error in a calorie target. Most people who describe themselves as "very active" are moderately active by the standard definitions, and a one-step overestimate adds roughly 300 calories a day — enough to turn a deficit into maintenance.
Every result on this shelf is a population estimate. They are starting points to test against what actually happens over three or four weeks, not prescriptions. Nothing here is a diagnosis, and nothing here should replace a conversation with a doctor or a registered dietitian.
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Health questions
None of them, initially. Take the TDEE calculator's figure as a starting hypothesis, eat to it consistently for three weeks, and adjust based on what the scale actually does. Formula-based estimates are typically within 10–15% for most people, which is enough to matter.
No, but it is narrow. It is a good population screen and a poor individual verdict, and it misclassifies muscular and older people in opposite directions. Pair it with waist circumference or the body fat calculator and it becomes genuinely informative.
Common evidence-based bands run from about 0.8 g per kilogram of body weight for sedentary adults to 1.6–2.2 g/kg for people training hard or in a calorie deficit. The protein calculator sets a target within those bands and splits it across meals.
No. Adult BMI cut-offs do not apply to anyone under 20, who should be assessed against age-and-sex percentile charts. Energy and fluid requirements in pregnancy and breastfeeding differ substantially from the formulas used here. Speak to a clinician.
Typically within three to four percentage points of a DEXA scan for most people, which is good for a tape measure and poor compared with a laboratory. Its real strength is consistency — measure the same way each time and the trend is reliable even if the absolute number is not.
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