Free health & fitness calculators you can trust — clear tools backed by standard formulas and a medical reviewer.
ZelsawCalc publishes free, easy-to-use health and fitness calculators alongside plain-English guides. Our goal is to help you understand the numbers behind your body — BMI, body fat, calorie needs, macros, heart-rate zones, pace, and pregnancy timing — using the same standard formulas clinicians and researchers rely on.
Every calculator uses a published, widely accepted formula, and we name the method on each page so you can check our work:
Maya is a health and science writer focused on translating research on nutrition, fitness, and body composition into practical, non-alarmist guidance. She writes the majority of our calculator guides.
Sofia is a registered dietitian who contributes and reviews our nutrition and weight-management content, keeping calorie and macro guidance aligned with mainstream dietetic practice.
Dr. Patel is a licensed physician who medically reviews our calculators and guides for accuracy and safety. Medical review confirms that the formulas, ranges, and health context we present reflect current, mainstream medical understanding. It is not a substitute for individual medical advice.
ZelsawCalc is free to use and supported by advertising. Advertising never influences the formulas we use or the guidance we give. See our Editorial & Medical Review Policy for details.
Questions, corrections, or feedback? Visit our contact page or email contact@zelsaw.com.
This tool is for general informational and educational purposes only and is not medical advice. It does not diagnose, treat, or replace care from a qualified professional. Always consult a physician or other qualified healthcare provider about your individual health.