Health Calculators

BMI, Calories, Sleep, Heart Rate and more. Instant results, no sign up.

Water Intake Calculator

How much water you should drink daily

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Ideal Weight Calculator

Healthy weight range for your height

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What are these health calculators, and who needs them?

This page brings together seven simple tools that turn a few personal details, such as age, height and weight, into numbers you can act on: BMI, daily calories, water intake, bedtime, heart rate zones, ideal weight range and body fat percentage. They help people starting a fitness routine, anyone trying to lose or gain weight, students and professionals fixing their sleep, and families who want a quick reference before a doctor visit.

Formulas behind the calculators

BMI = weight (kg) ÷ height (m) squared
Calories: BMR (Mifflin-St Jeor) = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. Daily needs = BMR × an activity factor, from 1.2 for a desk job to about 1.9 for very hard training
Maximum heart rate = 220 − age, with training zones taken as percentages of that figure
Sleep: a cycle lasts about 90 minutes, and most people need 5 or 6 cycles plus around 15 minutes to fall asleep
Water: a common rule of thumb is 30 to 35 ml per kg of body weight, more in heat or with exercise

Worked example

Take a 30-year-old man who weighs 70 kg and is 170 cm (1.70 m) tall. His BMI is 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.2. That is in the normal range on the global WHO scale, but it falls in the overweight band on Indian and Asian cut-offs, which start at 23.

His BMR is 10 × 70 + 6.25 × 170 − 5 × 30 + 5 = 700 + 1,062.5 − 150 + 5 = 1,617.5 calories. With moderate exercise (factor 1.55) his daily need is about 2,507 calories. His maximum heart rate is 220 − 30 = 190 beats per minute. If he wakes at 6:30 am and wants 5 sleep cycles (7.5 hours) plus 15 minutes to fall asleep, he should be in bed by 10:45 pm.

Frequently asked questions

Which health calculator should I start with?

Start with the BMI calculator for a quick check of your weight against your height. If your goal is to lose or gain weight, move on to the calorie calculator. The water, sleep and heart rate tools are useful for daily habits and exercise.

Are BMI cut-offs different for Indians?

Yes. The global WHO table calls a BMI of 25 overweight and 30 obese. Indian and Asian guidelines use lower limits, with overweight from 23 and obesity from 25, because South Asians tend to carry more body fat at the same BMI. Discuss your result with a doctor.

Are these health calculators free to use?

Yes. All the calculators are free, work instantly in your browser and need no sign up.

How accurate are the calorie and heart rate results?

They are estimates based on averages. Two people with the same age, height and weight can differ by several hundred calories a day, and maximum heart rate can vary by 10 beats or more. Treat the numbers as a starting point and adjust based on how your body responds.

Can I use these results to diagnose a health problem?

No. These tools give general estimates and cannot diagnose or treat any condition. If you have a medical condition, are pregnant, or are making a big change to your diet or exercise, speak to a qualified doctor or dietitian first.

Limitations and accuracy

BMI cannot tell muscle from fat, so athletes can appear overweight. It is also less reliable for children, older adults and pregnant women. Calorie, heart rate and water figures are population averages and do not account for medical conditions, medication, climate or body composition. This page is for general information only and is not medical advice.