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HealthCalc
35 Free Science-Backed Tools

Know your body.
Exactly.

Free health calculators powered by peer-reviewed science — Water weight cuts, TDEE, macros, body fat, biological age & 30 more. Instant results, zero sign-up.

No Sign-UpClinically ValidatedMetric & Imperial100% Free
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Free Health & Fitness Calculators

Search, sort, and filter our full suite of 35 science-backed wellness calculators instantly.

#1 Popular

Water Weight Cut

Performance & Fitness

Plan your fight week water cut with sport-specific protocols. Day-by-day loading, sodium timing, gut cut, and post-weigh-in rehydration.

Build Water Cut Plan

TDEE Calculator

Calorie & Energy

Estimate your Total Daily Energy Expenditure based on your physical features, daily activities, and exercise levels.

Calculate TDEE

Body Fat Calculator

Body Composition

Estimate your body fat percentage using Navy, YMCA, and skinfold caliper calculation methods side-by-side.

Calculate Body Fat

Calorie Deficit Calculator

Calorie & Energy

Establish a healthy calorie deficit target with an interactive timeline that projects safe weight loss week-by-week.

Calculate Deficit

Biological Age

Health & Vital Signs

Calculate your biological age using lifestyle factors, BMI, and resting heart rate. Includes what-if simulator, system ages, and personalized action plan.

Calculate Bio Age

Carnivore Diet Calculator

Nutrition & Diet

Zero-carb macro calculator with food equivalents, ratio explorer, adaptation timeline, troubleshooting engine, and meat cost estimator.

Calculate Carnivore Macros

BMR Calculator

Calorie & Energy

Determine your Basal Metabolic Rate—the calories your body burns at complete rest—using four distinct scientific models.

Calculate BMR

Ideal Weight Calculator

Body Composition

Determine your ideal body weight range using classic clinical equations (Devine, Robinson, Hamwi).

Calculate Ideal Weight

Lean Body Mass Calculator

Body Composition

Calculate your lean body mass (LBM) and FFMI score using Boer, James, Hume, and Katch-McArdle formulas.

Calculate LBM

FFMI Calculator

Body Composition

Calculate your Fat-Free Mass Index (FFMI) — raw and height-adjusted. Get natural muscle potential estimate, body composition, and what-if simulator.

Calculate FFMI

Cutting Calculator

Calorie & Energy

Bodybuilding cutting prep with calorie limits, muscle preservation limits, and interactive timelines.

Start Cutting Plan

One Rep Max Calculator

Performance & Fitness

Estimate your maximum lifting capacities (squat, bench press, deadlift) with 5 scientific models.

Calculate 1RM

Intermittent Fasting Calculator

Nutrition & Diet

Plan your fasting schedule with personalized eating windows, sleep overlap analysis, and protein-per-meal targets. Supports all major protocols.

Plan My Fasting

Macro Calculator

Nutrition & Diet

Find your personalized macronutrient split. Get exact gram targets for proteins, carbohydrates, and healthy fats.

Calculate Macros

Waist-to-Hip Ratio

Body Composition

Calculate your Waist-to-Hip Ratio with body shape classification, health risk assessment, and ideal proportion analysis.

Calculate WHR

Reverse Diet Calculator

Calorie & Energy

Build a week-by-week calorie roadmap to recover your metabolism after a cut, with fat gain risk scoring and a water retention explainer.

Build Reverse Diet Plan

Carb Cycling Calculator

Nutrition & Diet

Create a custom weekly carb cycling plan. Estimate high, low, and no-carb day macros in grams.

Calculate Carb Cycling

Pediatric Growth Chart

Family & Growth

Calculate infant and child percentiles for weight, height, BMI, and head circumference. Map growth curves and simulate trajectories.

Calculate Child Growth

Blood Pressure Calculator

Health & Vital Signs

Check your blood pressure reading instantly. Get BP category, MAP, pulse pressure, 7-day averages, age comparison, and trend tracking.

Check BP Reading

Grip Strength

Performance & Fitness

Find your grip strength percentile by age and gender. Includes longevity risk, EWGSOP2 sarcopenia screening, and improvement targets.

Test Grip Strength

Sleep Calculator

Health & Vital Signs

Find your optimal bedtime or wake-up time using 90-minute sleep cycles and age-based sleep duration recommendations.

Calculate Sleep Times

Waist-to-Height Ratio

Body Composition

Calculate your Waist-to-Height Ratio (WHtR) with standard and military compliance modes. Health risk category, body shape analysis, and what-if simulator.

Calculate WHtR

Protein Intake Calculator

Nutrition & Diet

Calculate your optimal daily protein intake for muscle gain, fat loss, or maintenance with GLP-1 support.

Calculate Protein

BMI Calculator

Body Composition

Calculate Body Mass Index (BMI) for adults and kids. Includes child percentiles, Trefethen formula, and body fat/FFMI adjustments.

Calculate BMI

RMR Calculator

Calorie & Energy

Calculate your true Resting Metabolic Rate (RMR) with clinical formulas (Mifflin-St Jeor, Cunningham). Factors in lean body mass, lifestyle, sleep, and metabolic adaptation.

Calculate RMR

Zone 2 Heart Rate

Performance & Fitness

Find your Zone 2 heart rate using %MHR or Karvonen methods. Compare formulas, view all 5 zones, and classify any heart rate reading.

Find Zone 2 HR

HRV Calculator

Health & Vital Signs

Enter your rMSSD or SDNN from Oura, WHOOP, Garmin, or Apple Watch. Get your age-sex percentile, ANS balance, lifestyle impact score, and daily recovery recommendations.

Analyze My HRV

Due Date Calculator

Family & Growth

Calculate your estimated due date, current pregnancy week, and trimester using LMP, conception, IVF or ultrasound dating.

Calculate Due Date

VO2 Max Calculator

Performance & Fitness

Estimate VO2 max without a wearable. 4 test methods: Cooper run, Rockport walk, George jog, or no-exercise estimate. Get cardio age, ACSM classification, and training zones.

Calculate VO2 Max

Water Intake Calculator

Nutrition & Diet

Calculate daily water needs adjusted for body parameters, training, climate, and creatine supplements.

Calculate Water

Ovulation Calculator

Family & Growth

Calculate your ovulation date and fertile window. Confidence-based predictions with optional BBT, LH test, and cervical mucus tracking.

Track Ovulation

Ramadan Fasting Calculator

Calorie & Energy

Plan your Ramadan nutrition with adjusted fasting TDEE, personalized meal targets, and hydration goals.

Calculate Ramadan Calories
New

Keto Macro Calculator

Nutrition & Diet

Personalized daily keto macros for fat loss or muscle recomp. Calculates net carbs limits, lean mass protein goals, fat levers, and keto flu electrolyte targets.

Calculate Keto Macros
New

Body Recomposition Calculator

Body Composition

Build muscle and lose body fat simultaneously. Calculates workout vs. rest day calorie cycling and a 12-week transformation roadmap.

Calculate Recomposition
New

PSMF Calculator

Nutrition & Diet

Calculate your Protein Sparing Modified Fast macros, Lyle McDonald category (1, 2, or 3), refeeds, and electrolyte shield.

Calculate PSMF

Featured Online Fitness Calculators

Deep dive into our top-performing tools designed for athletic performance, calorie tracking, and body composition.

#1 Top Performer · Combat Sports

Water Weight Cut Protocol

Sport-specific weight cutting calculator for MMA fighters, wrestlers, and powerlifters. Features daily water loading, sodium manipulation, gut flush timing, and safe post-weigh-in rehydration schedules.

Build Water Cut Plan →
Flagship · Calorie Tracking

TDEE & Energy Tracking

Calculates your Total Daily Energy Expenditure using Mifflin-St Jeor, Revised Harris-Benedict, and Katch-McArdle models. Maps physical activity levels to set precise fat loss, maintenance, or muscle building calories.

Calculate TDEE →
Multi-Method · Body Composition

Body Fat Percentage

Compare US Navy tape circumference, YMCA fat index, and Jackson-Pollock 3-Site skinfold caliper methods side-by-side. Visualizes fat mass, lean tissue mass, and athletic body composition ranges.

Calculate Body Fat →

How to Use Our Free Health Tools

Follow these three steps to estimate your body composition and dietary targets.

1

Choose Your Calculator

Select a tool tailored to your goal, whether it is cutting weight for competition, tracking daily caloric expenditure, or estimating body fat.

2

Input Your Metrics

Toggle between metric and imperial units. Enter your height, weight, activity frequency, and body measurements safely.

3

Get Instant Results

Receive detailed, science-backed summaries, classifications, and target timelines without completing any signup form.

Why Choose HealthCalc as Your Health Calc?

At HealthCalc, we believe that every health calculator — whether you call it a health calc or a fitness calculator — should be simple, accurate, and completely free. Unlike platforms that lock calculations behind paywalls or force complex signups, we offer free health calculators with zero friction.

Our Health Calc suite — water weight cut calculator, TDEE calculator, BMR calculator, calorie deficit calculator, macro calculator, and body fat percentage calculator — uses clinically validated formulas like Mifflin-St Jeor, revised Harris-Benedict, and the US Navy Method. Whether you are adjusting daily calorie targets for weight loss, calculating macros for muscle building, or estimating body fat, our health calculators support both metric and imperial units.

We provide instant, reliable health and fitness insights grounded in scientific literature, helping you make informed decisions for your wellness journey.

Frequently Asked Questions

Common questions about our online health and fitness calculators.

Are these health and fitness calculators free to use?
Yes, all calculators on HealthCalc are 100% free with no signup, email verification, or paid accounts required. Our goal is to provide accessible, high-quality tools for everyone.
How accurate are these online fitness calculators?
Our tools use gold-standard, peer-reviewed scientific formulas like Mifflin-St Jeor, Harris-Benedict, Katch-McArdle, and the US Navy Method. While they provide highly reliable estimates, they are intended for informational purposes and should not replace clinical medical advice.
Can I use these health calculators for weight loss?
Absolutely. Tools like the Water Weight Cut Calculator, TDEE Calculator, Calorie Deficit Calculator, and Macro Calculator are specifically designed to help you determine your daily energy requirements, weight cutting timelines, and macronutrient targets.
Do you save my health data or personal information?
No. We respect your privacy. All calculations are performed instantly in your browser (clientside), and we never store, track, or share your personal health metrics.
Do these calculators support both metric and imperial units?
Yes, all our tools fully support both metric and imperial units, making it easy to input your weight, height, and body measurements in whatever unit system you prefer.
What formulas do you use for body fat percentage calculation?
Our free body fat calculator uses multiple proven methods simultaneously, including the US Navy Method (circumference measurements), Jackson-Pollock 3-Site skinfold formula, and the YMCA method, giving you a comprehensive overview of your body composition.