Health & fitness calculators

Quick, private body and nutrition tools — metric or imperial, no sign-up.

These tools turn the standard formulas used in health and fitness — BMI, the Mifflin-St Jeor equation for metabolism, the U.S. Navy body-fat method and others — into quick answers. Switch between metric and imperial units, enter a few numbers, and get a clear result plus the category or healthy range it falls in. Nothing is stored; every calculation runs privately in your browser.

They're useful for tracking progress and understanding the numbers, but they're general estimates, not a medical assessment.

BMI Calculator
Body mass index, your weight category and a healthy range for your height.
Calorie Calculator
Daily calorie needs (TDEE) plus targets to lose, maintain or gain.
BMR Calculator
Calories your body burns at rest, via the Mifflin-St Jeor equation.
Body Fat Calculator
Body fat percentage and category by the U.S. Navy tape method.
Ideal Weight Calculator
Ideal body weight by four classic formulas, plus a healthy range.
Macro Calculator
Daily protein, carb and fat targets in grams for your goal.
Pregnancy Due Date Calculator
Estimate your due date, how far along you are and your trimester.
Water Intake Calculator
How much water to drink a day, in litres, cups and ounces.
Heart Rate Zone Calculator
Your max heart rate and five training zones from your age.
Waist-to-Hip Ratio Calculator
Your WHR and the WHO health-risk category for your sex.
Protein Intake Calculator
Daily protein target in grams for your weight and goal.

Which health calculator do you need?

Weight & body composition: BMI, Body Fat, Ideal Weight and Waist-to-Hip Ratio.

Calories & nutrition: the Calorie (TDEE) and BMR calculators for daily energy needs, plus Macros and Protein for what to eat.

Fitness & everyday: Heart Rate Zones for training and the Water Intake calculator. Expecting? The Pregnancy Due Date Calculator estimates your due date and trimester.

Last updated: July 2026 · How we calculate

BriskToolbox health tools provide general estimates for information only and are not medical advice. Consult a qualified healthcare professional for personal guidance.

Frequently asked questions

How accurate are these health calculators?

They use well-established formulas and give reliable estimates for most people, but they're general tools. Individual factors — muscle mass, body frame, medical conditions — can move the real figure. Use them for guidance, not diagnosis.

Metric or imperial — which should I use?

Either. Every health calculator here has a unit toggle, so you can enter centimetres and kilograms or feet, inches and pounds, and the result is the same.

Do you store my measurements?

No. All calculations run in your browser; nothing you enter is sent to or saved on our servers.

Should I rely on these instead of seeing a doctor?

No. These calculators are for general information only and aren't medical advice. For health decisions, talk to a qualified healthcare professional.