Health calculators based on trusted public guidelines

Free, fast health and fitness calculators — BMI, daily calories, sleep, hydration, heart-rate zones and more. Built on recognized public guidelines, with every formula and its limits explained. Educational only, not medical advice.

In short

AllHealthCalc offers 10 free health and fitness calculators — BMI, calorie/TDEE, ideal weight, waist-to-height, heart-rate zones, steps-to-calories, water intake, sleep, period tracking, and a stress check-in — each built on a published formula or public-health guideline (WHO, Mifflin-St Jeor, Karvonen).

Every calculation runs entirely in your browser with no sign-up and no data stored. The tools give educational estimates, not medical advice.

Choose a calculator

BMI Calculator Body Mass Index with WHO categories and your healthy weight range. Calorie / TDEE Calculator Daily calorie needs from BMR and activity level. Ideal Weight Calculator A healthy weight range from four classic formulas. Waist-to-Height Ratio A quick screen for central body fat. Heart Rate Zones Five training zones via the Karvonen method. Steps to Calories Distance and calories burned from your step count. Water Intake Calculator A daily hydration estimate from weight and activity. Sleep Calculator Best bedtime and wake times by 90-minute cycle. Period Tracker Predict your cycle — saved only on your device. Stress Check-in A private, non-diagnostic self-reflection.

Which calculator should you start with?

The ten tools here answer different questions, and the right starting point depends on what you're trying to understand. If your goal is a general read on body weight, begin with the BMI calculator for the standard screening figure, then check the waist-to-height ratio — the second matters because where you carry weight affects metabolic risk more than total weight alone, and the two together tell a fuller story than either by itself.

If your goal is changing your weight, the calorie/TDEE calculator is the anchor: it estimates how many calories you burn in a day, which is the number any gain or loss plan works from. Pair it with the ideal weight calculator for a target range and the steps-to-calories tool to see what daily movement adds. If your goal is training better, the heart-rate zones calculator turns a single max-heart-rate estimate into five effort bands you can actually train by. And if you're focused on recovery and daily habits, the sleep and water intake calculators translate general guidelines into concrete times and amounts for your body.

How we build these tools

Every calculator on this site is built on a published, recognized formula or public-health guideline — the WHO definition of BMI, the Mifflin-St Jeor equation for metabolic rate, the Karvonen method for heart-rate zones — and each tool's page names the formula it uses and links to the source where practical. We show the math rather than hiding it behind a black box, because a number you understand is one you can question.

We are equally deliberate about limits. Health calculators work on population averages, and an average is exactly the wrong tool for telling you something about a specific person's body. That's why every result here comes with the conditions under which it misleads: BMI can't tell muscle from fat, calorie estimates carry a real margin of error, and a hydration formula can't know your climate or medications. Read on each page is a section on when to stop trusting the number and talk to a professional.

All calculations run entirely in your browser. We store nothing, require no sign-up, and never transmit your inputs — the period tracker's history, for instance, lives only in your device's local storage. The site is built and maintained by Gong Baolin at WisePath Technology LLC, and supported by unobtrusive advertising so it can stay free. Nothing here is medical advice; it is educational information to help you have better-informed conversations with qualified providers.