A calculator site with no interest in your data

Wellnum started from a simple frustration: most health calculators online are wrapped in five layers of pop-ups, autoplay video, and "sign up to see your result" walls, just to hand you a number you could work out with a formula and a calculator app.

So this is the opposite bet — four calculators (BMI, BMR, daily calories, and water intake), built on standard, published formulas, that show their working and get out of your way. Nothing is stored, no account is required, and the maths runs entirely in your browser.

The formulas we use

BMI follows the World Health Organization's standard weight ÷ height² calculation. BMR uses the Mifflin-St Jeor equation, generally considered more accurate than the older Harris-Benedict formula. Daily calorie needs apply standard activity multipliers on top of BMR. Water intake starts from a per-kilogram baseline with adjustments for exercise and climate. None of these numbers are medical advice — they're well-established estimates, and you should treat them as a starting point, not a prescription.

Who's behind it

Wellnum is an independent, small-scale project. If something looks wrong or you'd like a calculator we don't have yet, get in touch.