Our health calculators turn a few simple measurements into useful information about your weight, energy needs, hydration and pregnancy. They follow published medical formulas and guidelines from organisations such as the WHO, NHS and CDC, show you how each result is worked out, and run privately in your browser.

Body Weight and BMI

The BMI calculator gives your Body Mass Index with both the international and Asian-Indian categories, plus your healthy weight range and BMR. UK users can enter stones and pounds in the BMI calculator UK, which also checks waist-to-height ratio. The ideal weight calculator compares the best-known formulas for your height.

Calories, Energy and Hydration

Find how many calories you need with the calorie calculator or the more detailed TDEE calculator, which uses your activity level to estimate total daily energy expenditure for weight loss, maintenance or muscle gain. The water intake calculator estimates how much you should drink based on your weight, activity and climate.

Pregnancy, Children and Clinical Tools

Expecting parents can use the pregnancy calculator to find the due date and current week. The height calculator predicts a child's adult height from the parents' heights, and the Poshan calculator checks growth for children under five using WHO standards. For clinicians, the MME calculator converts opioid doses to morphine milligram equivalents using CDC 2022 factors.

Use Results Wisely

Health calculators give estimates for the average adult. They cannot account for your medical history, medicines, pregnancy complications or conditions such as diabetes or kidney disease. Use them to start a conversation with your doctor, dietitian or midwife – not to replace one.

Frequently Asked Questions

Are these health calculators accurate?

They use standard, published formulas such as the WHO BMI categories and the Mifflin-St Jeor equation. Results are good estimates for most adults but are not a medical diagnosis.

Which BMI categories do you use for Indians?

The BMI calculator shows both the WHO international categories and the lower Asian-Indian cut-offs, where overweight starts at a BMI of 23.

Is my health information stored?

No. Everything is calculated in your browser and nothing you enter is sent to our server.

Can I use these tools for children?

The adult BMI and calorie tools are for adults. For children under five, use the Poshan calculator, which follows the WHO Child Growth Standards.