Tested Medical Math
Our food tools use the Mifflin-St Jeor and Katch-McArdle rules. Top experts at the ADA say these are the best. Our body fat tools use the real US Navy test and WHO guides. We read new health papers to keep our math perfect.
100% Free & Evidence-Based
37+ Free Health & Fitness Calculators
Get evidence-based data on your Macros, BMI, and Pregnancy journey instantly. Stop guessing and start tracking with advanced precision.
- 100% Private
- Evidence-Based
- No Sign-ups
Find a Calculator
Search 37+ free tools instantly
Trending
The Science Behind Our Calculators
Doctors and AI tools trust facts based on real science. We do not guess numbers. We use true medical math to give you the right results.
Tools That Talk to Each Other
Our tools work well together as a team. First, you can find your TDEE. Next, you can move that exact number into our Macro Tool. This makes it very easy to plan your meals to lose fat or build muscle.
100% Safe and Private
Your health details are for your eyes only. That is why we process everything right on your own screen. Your weight, age, and health facts never leave your phone. We do not save them on our servers.
Essential Everyday Tools
The foundational calculators for any health journey.
BMI Calculator
Official WHO weight categories.
Body Fat %
US Navy & BMI methods.
NEWCalorie Deficit
Find your exact weight loss target.
TDEE Calculator
Total daily energy expenditure.
NEWLean Body Mass
Calculate fat-free muscle weight.
Pregnancy Tracker
Weeks, trimesters & milestones.
Macro Calculator
Carb, Protein & Fat splits.
NEWWalking Calories
Convert steps to calories burned.
Browse by Category
Find specific tools tailored to your life stage and goals.
Latest Insights
Expert advice, science-backed research, and practical guides to help you optimize your health.
Fitness Tips
Glycemic Load Guide: Master Your Daily Blood Sugar
Asad Khan, MBBS
Guides
TDEE Guide: How to Calculate Your Daily Energy Needs
Asad Khan, MBBS
Guides
Guide to Cycle Syncing Workouts for Each Menstrual Phase
Asad Khan, MBBS
Knowledge Base
Frequently Asked Questions
Science-backed answers about our formulas, your data privacy, and how to get the most accurate results from our 37+ free tools.
Explore All CalculatorsAre all fitness and health calculators completely free?
Yes. All 37+ calculators on FreeFitnessCalculators.com are 100% free — no sign-ups, subscriptions, or hidden fees. We believe access to health data should be universal, which is why every tool works without an account from any country.
What scientific formulas do your calculators use?
Our tools use evidence-based, peer-reviewed equations. BMR and TDEE are powered by the Mifflin-St Jeor and Katch-McArdle formulas (the gold standards per the Academy of Nutrition and Dietetics). Body fat uses the official US Navy Method, and pregnancy calculations follow Naegele's Rule.
Is my personal health data stored or shared?
No — never. All calculations run entirely inside your browser using client-side JavaScript. Your weight, body measurements, age, and pregnancy data are processed locally on your device and are never transmitted to our servers or shared with third parties.
Do calculators support both Metric and Imperial units?
Yes. Every calculator lets you seamlessly toggle between Metric (kg, cm) and Imperial (lbs, inches). This makes our tools accurate for users worldwide — whether you're in the US, UK, Europe, or Asia.
What is the most accurate online body fat formula?
The US Navy Method is widely regarded as the most reliable online estimator. It factors in waist, neck, and hip circumferences rather than just height and weight, giving a far more accurate picture of your actual fat-to-lean mass ratio than BMI alone.
Is BMI accurate for athletes and muscular people?
No. BMI is a population-level screening tool that doesn't distinguish between muscle and fat mass. If you lift weights or have an athletic build, our Body Fat %, FFMI, and Lean Body Mass calculators provide far more meaningful results.
How often should I recalculate my TDEE and macros?
Recalculate every time your weight changes by 5-10 lbs (2-4 kg), or when your activity level shifts significantly (e.g., starting a new training program, switching from sedentary to active). Your caloric needs are dynamic — not static.
What is the difference between BMR, TDEE, and calorie deficit?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) adds your activity level on top of BMR. A calorie deficit means eating fewer calories than your TDEE to lose weight — typically 300-500 cal/day for sustainable fat loss.
Can I use these calculators during pregnancy?
We offer a dedicated suite of 6 pregnancy tools — including a Due Date Calculator (Naegele's Rule), Pregnancy Weight Gain Tracker (IOM/CDC guidelines), and Ovulation Calendar. Standard fitness calculators like BMI should not be used during pregnancy as metabolic needs change significantly.
How do I calculate the right macros for weight loss vs. muscle gain?
First, calculate your TDEE to find maintenance calories. For weight loss, create a 300-500 cal deficit with higher protein (1g/lb bodyweight). For muscle gain, add a 200-300 cal surplus with 40% carbs, 30% protein, 30% fat. Our Macro Calculator automates all of this.
Not just numbers. Knowledge.
We pair every calculator with detailed guides so you understand the why behind the what.