FitCalc is a collection of free, science-backed fitness calculators designed to help you make informed decisions about your training and nutrition. Every calculator on this site uses peer-reviewed scientific formulas from published research, and every article is based on evidence from the sports science and nutrition literature.
Our Mission
The fitness and nutrition space is full of marketing masquerading as advice. FitCalc exists to provide clear, accurate, free tools that help you cut through the noise and make decisions based on actual science. No sign-ups, no paywalls, no affiliate-driven product pushes, no extreme claims.
We believe that understanding the math behind your body — how many calories you burn, how much protein you need, what your training percentages should be — is the foundation of any successful fitness plan. The calculators and guides here give you that foundation.
Editorial Standards
Every calculator and article on FitCalc follows these standards:
- Peer-reviewed formulas. Every calculator uses equations from published research, clearly cited and explained. We use Mifflin-St Jeor for BMR (as recommended by the Academy of Nutrition and Dietetics), the US Navy method for body fat estimation, Epley/Brzycki/Lombardi for 1RM estimation, and similar well-validated formulas elsewhere.
- Transparent methodology. Every calculator shows the formulas used. You can verify the math yourself, or use our numbers as a sanity check against other sources.
- Evidence-based content. Blog articles and educational sections cite specific research where possible and reflect current scientific consensus. When research is contested, we say so.
- Practical, honest advice.We don't overstate what calculators can do. These tools give you estimates, not certainties, and we're clear about the limitations.
- No pseudoscience.You won't find detox teas, fat-burning spot reduction myths, or magic timing windows here. Just the actual science.
Our Tools
Eight calculators covering the core of fitness math:
Nutrition
- TDEE Calculator— Total Daily Energy Expenditure using the Mifflin-St Jeor equation.
- Macro Calculator— Daily protein, carbs, and fat targets based on your goals and diet style.
- Protein Calculator— Evidence-based protein intake recommendations based on your body weight and activity level.
- Calorie Deficit Calculator — Plan your weight loss with a daily calorie target and timeline estimate.
Body Composition
- BMI Calculator— Body Mass Index with context on its strengths and limitations.
- Body Fat Calculator — US Navy method estimation of body fat percentage.
- Ideal Weight Calculator — Four medical formulas for estimating ideal body weight.
Strength
- One-Rep Max Calculator — Estimate your 1RM using three validated formulas with training percentage charts.
How to Use FitCalc
Most users benefit from a combination of calculators. Here are the most common paths:
- Weight loss path: TDEE → Calorie Deficit → Macros
- Muscle building path: TDEE → Protein → 1RM
- Health check path: BMI → Body Fat % → Ideal Weight
Our Content
In addition to calculators, we publish long-form educational content on topics like how to calculate your TDEE, the real science of protein intake, what a calorie deficit actually is, BMI vs. body fat percentage, and more. Every article is written to be accurate first, helpful second, and SEO-optimized third (in that order).
Privacy First
All calculations happen entirely in your browser. We never see, store, or transmit the values you enter into our calculators. No accounts, no sign-ups, no data collection on your inputs. We use standard analytics (Google Analytics) to understand site usage in aggregate and show advertisements (Google AdSense) to support the free tools. See our Privacy Policy for full details.
Medical Disclaimer
FitCalc is for informational and educational purposes only. The results provided by our calculators are estimates based on scientific formulas and should not be considered medical advice. Individual results vary significantly based on factors our calculators cannot account for, including medical conditions, medications, body composition details, and genetic factors.
Always consult with a qualified healthcare professional, registered dietitian, or certified trainer before starting any new diet, exercise program, or significantly changing your caloric intake. Never disregard professional medical advice or delay seeking it because of information on this site. See our Terms of Service for full legal terms.
Feedback and Corrections
We actively welcome corrections, suggestions, and feedback. If you find an error in a calculator or article, or if research in an area has advanced beyond what we describe, please let us know at contact@fitcalc.health. Science evolves, and we update our content when warranted.
Accessibility
FitCalc is designed to be accessible. All calculators work on mobile devices, all content is readable with screen readers, and no calculator requires JavaScript features beyond basic form submission. Pages load in under a second on typical connections. No registration required — the calculators work for anyone who can open a web page.