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64 free health calculators · 30 personalised meal plans · 4 guided journeys · workout planner. Evidence-based science, instant results, no sign-up.
🍽️ 30 Free 7-Day Personalised Meal Plans
Keto · Vegan · Weight Loss · Muscle Gain · Gut Health · DASH · Mediterranean + more
Featured Calculators
Our most-used science-backed tools — rendered server-side for instant load
BMI Calculator
Calculate your Body Mass Index using the WHO standard formula. Get your weight category and healthy weight range instantly.
BMI = weight(kg) / height(m)²
Calorie Calculator
Calculate your BMR and TDEE using the Mifflin-St Jeor equation. Get personalized daily calorie targets for any goal.
Mifflin-St Jeor × Activity Multiplier
TDEE Calculator
Calculate your Total Daily Energy Expenditure. The most important number for setting any nutrition goal.
TDEE = BMR × Activity Multiplier
Macro Calculator
Calculate your optimal protein, carbohydrate, and fat targets based on your calorie goal and fitness objective.
Protein 1.6–2.2g/kg · Carbs & Fat fill remaining calories
Weight Loss Calculator
Calculate how long it will take to reach your goal weight, your required daily calorie deficit, and your projected weekly fat loss rate.
Weeks = (weight diff × 7700) / (deficit × 7)
Muscle Gain Calculator
Calculate your optimal calorie surplus for lean muscle gain, your natural muscle-building potential, and required protein intake.
Surplus = TDEE + 250–500 kcal; Monthly gain by experience level
Browse by Category
Find the right calculator for your health goal
Health Calculators
Science-backed health metrics and body composition calculators.
Nutrition Calculators
Precision nutrition calculators for calories, macros, and dietary targets.
Fitness Calculators
Performance and training calculators for athletes and fitness enthusiasts.
Lifestyle Calculators
Everyday wellness and lifestyle calculators.
Unit Converters
Fast, accurate unit conversions for fitness and nutrition.
What's your goal today?
Pick a goal and we'll filter the tools that matter most for you.
BMI Calculator
Calculate your Body Mass Index using the WHO standard formula. Get your weight category and healthy weight range instantly.
Calorie Calculator
Calculate your BMR and TDEE using the Mifflin-St Jeor equation. Get personalized daily calorie targets for any goal.
TDEE Calculator
Calculate your Total Daily Energy Expenditure. The most important number for setting any nutrition goal.
Macro Calculator
Calculate your optimal protein, carbohydrate, and fat targets based on your calorie goal and fitness objective.
Calorie Deficit Calculator
Calculate your daily calorie deficit to lose weight at a safe, sustainable rate without sacrificing muscle.
Ideal Weight Calculator
Find your healthy weight range based on height, age, and gender using multiple validated formulas.
Protein Intake Calculator
Calculate your optimal daily protein intake based on body weight, goal, and activity level.
Water Intake Calculator
Calculate your optimal daily water intake based on body weight, climate, and activity level.
Body Fat Calculator
Estimate your body fat percentage using the US Navy method or BMI-based method.
Kg to Lbs Converter
Convert kilograms to pounds instantly. Simple, accurate kg to lbs conversion.
Lbs to Kg Converter
Convert pounds to kilograms instantly. Accurate lbs to kg conversion.
Kg to Stone Converter
Convert kilograms to stone and pounds. Popular with UK users.
Cm to Feet Converter
Convert centimetres to feet and inches instantly. Essential for height conversions.
BMR Calculator
Calculate your Basal Metabolic Rate — the calories your body burns at complete rest.
BMI Prime Calculator
Calculate your BMI Prime — a ratio of your BMI to the upper ideal BMI of 25.
Navy Body Fat Calculator
Calculate body fat percentage using the official US Navy circumference measurement method.
Waist to Hip Ratio Calculator
Calculate your waist-to-hip ratio to assess cardiovascular and metabolic health risk.
Heart Rate Zone Calculator
Calculate your 5 heart rate training zones based on your maximum heart rate.
One Rep Max Calculator
Calculate your one rep maximum (1RM) for any lift using multiple validated formulas.
Calories Burned Calculator
Calculate calories burned during exercise based on activity, duration, and body weight.
VO2 Max Calculator
Estimate your VO2 max — the gold standard of cardiovascular fitness — from running pace.
Running Calorie Calculator
Calculate calories burned running based on distance, speed, and body weight.
Running Pace Calculator
Calculate running pace, time, or distance. Essential for training and race planning.
Steps to Calories Calculator
Convert your daily step count to calories burned based on height, weight, and stride.
Body Shape Calculator
Determine your body shape (apple, pear, hourglass, rectangle) from measurements.
Body Surface Area Calculator
Calculate body surface area (BSA) using the DuBois, Mosteller, and Haycock formulas.
Blood Pressure Calculator
Interpret your blood pressure reading and understand your cardiovascular health status.
Cholesterol Calculator
Interpret your cholesterol levels and understand your cardiovascular risk.
Sleep Cycle Calculator
Calculate optimal sleep and wake times based on 90-minute sleep cycle science.
Age Calculator
Calculate exact age in years, months, days, and more from a birth date.
Caffeine Calculator
Calculate safe daily caffeine limits and estimate how long caffeine stays in your system.
Intermittent Fasting Calculator
Calculate your eating and fasting windows for different intermittent fasting protocols.
Pregnancy Due Date Calculator
Calculate your estimated due date from your last menstrual period or conception date.
Pregnancy Weight Gain Calculator
Calculate recommended pregnancy weight gain based on pre-pregnancy BMI using IOM guidelines.
Alcohol Calorie Calculator
Calculate calories from alcoholic drinks and understand their impact on your daily calorie budget.
Creatine Calculator
Calculate your optimal creatine dosage for loading and maintenance phases.
Vitamin D Calculator
Estimate your vitamin D requirements based on sun exposure, skin tone, and location.
Body Measurements Calculator
Calculate and track key body measurements including lean mass, body fat, and shape ratios.
Fibre Intake Calculator
Calculate your recommended daily fibre intake based on age, sex, and calorie needs.
Keto Macro Calculator
Calculate ketogenic diet macros: high fat, moderate protein, very low carb targets.
Calorie Cycling Calculator
Plan your calorie cycling schedule with high and low calorie days to boost results.
Calorie Goal by Date Calculator
Calculate the daily calorie intake needed to reach your target weight by a specific date.
Weight Loss Calculator
Calculate how long it will take to reach your goal weight, your required daily calorie deficit, and your projected weekly fat loss rate.
Muscle Gain Calculator
Calculate your optimal calorie surplus for lean muscle gain, your natural muscle-building potential, and required protein intake.
Waist-to-Height Ratio Calculator
Calculate your waist-to-height ratio — a powerful predictor of cardiovascular and metabolic disease risk that outperforms BMI for detecting central obesity.
Daily Calorie Calculator
Find out exactly how many calories you need per day to lose weight, maintain, or build muscle — personalised to your stats and activity level.
Fat-Burning Heart Rate Calculator
Calculate your personalised fat-burning heart rate zone (60–70% max HR) and all 5 training zones to optimise cardio for fat loss or performance.
Healthy Weight Calculator
Find your healthy weight range using 5 validated methods — BMI range, Hamwi, Devine, Robinson, and Miller formulas — with frame size adjustments.
Sleep Calculator
Calculate the best times to fall asleep or wake up based on 90-minute sleep cycles. Wake at the right point to feel dramatically more refreshed.
Macro Ratio Calculator
Find the optimal macronutrient ratios for your goal — fat loss, muscle gain, keto, endurance, or maintenance — with daily gram targets.
TDEE Calculator for Women
Calculate your Total Daily Energy Expenditure as a woman — with female-specific metabolic differences, activity levels, and goal-based calorie targets.
Weight Maintenance Calories Calculator
Calculate exactly how many calories you need to maintain your current weight — your TDEE maintenance calories — to stay weight-stable.
Protein Calculator
Calculate your optimal daily protein intake in grams based on body weight, goal, and activity — with per-meal targets and food source examples.
Calorie Intake Calculator
Calculate your recommended daily calorie intake to reach your goal weight by your target date — with a week-by-week timeline and safety analysis.
BMI Calculator for Children & Teens
Calculate BMI for children and teenagers aged 2–20 using CDC age-and-sex-specific percentile charts. Children's BMI is interpreted differently from adult BMI.
Target Heart Rate Calculator
Calculate your target heart rate zones for every fitness goal — fat burning, aerobic fitness, anaerobic threshold, and maximum effort.
Metabolic Age Calculator
Calculate your metabolic age — how your BMR compares to the average for your age group. A lower metabolic age indicates a healthier, more efficient metabolism.
Calories Burned Exercise Calculator
Calculate calories burned during 40+ exercises including running, cycling, swimming, HIIT, strength training, yoga, and walking — personalised by weight.
Biological Age Calculator
Find out how old your body really is. Estimate your biological age from 12 lifestyle factors including exercise, sleep, stress, diet, and heart rate.
FFMI Calculator
Calculate your Fat-Free Mass Index — how much muscle you have relative to height. Discover where you sit vs the natural muscle ceiling documented in research.
Zone 2 Heart Rate Calculator
Find your Zone 2 heart rate using the Maffetone Method — the aerobic training zone for fat burning, mitochondrial health, and longevity.
Net Carbs Calculator
Calculate net carbs by subtracting fibre and sugar alcohols from total carbohydrates. Essential for keto and low-carb diets.
GLP-1 Nutrition Calculator
Adjusted protein, calorie, and micronutrient targets for Ozempic, Wegovy, Mounjaro and Zepbound users. Prevent muscle loss on GLP-1 medications.
Harris-Benedict Calculator
Calculate BMR using the original 1919 Harris-Benedict equation and the revised 1984 Roza-Shizgal formula. Compare with Mifflin-St Jeor.
Why FitFuel Tools?
Trusted health tools built with accuracy, privacy, and science in mind.
Evidence-Based
Every calculator uses peer-reviewed, clinically validated formulas — Mifflin-St Jeor, US Navy Method, WHO standards.
Instant Results
All calculations happen in real time in your browser. No loading, no waiting, no account needed.
Private by Design
Your health data never leaves your device. We never collect, store, or sell personal information.
Works Everywhere
Fully optimised for mobile, tablet, and desktop. Use all tools anywhere, anytime, even offline.
Personalised Plans
Save your stats once. Every tool — calculators, meal planner, workout planner — uses your saved profile.
30 Free Meal Plans
AI-powered 7-day meal plans personalised to your calorie target, macros, dietary preferences, and cuisine.
Workout Planner
Personalised workout plans for gym or home, matched to your experience level, goal, and schedule.
Guided Journeys
4 step-by-step guided journeys: Lose Weight, Gain Muscle, Maintain Weight, and Improve Nutrition.
Health Quizzes
Interactive quizzes to find your ideal diet, training style, and nutrition approach — no calorie counting required.
A Complete Health Calculation Suite
FitFuel Tools brings together the most important health and nutrition calculators plus 30 personalised meal plans in one clean, fast, and free platform.
Every calculator uses clinically validated formulas — the Mifflin-St Jeor equation powers our Calorie and TDEE calculators, the US Navy Method estimates body fat, and WHO classification standards underpin our BMI tool.
Our free meal planner creates personalised 7-day plans based on your goal, diet type, cuisine preference, and cooking style — downloadable in one click.
Most Popular Tools
The calculators our users reach for most
BMI
Calculate your Body Mass Index using the WHO standard formula. Get your weight category and healthy weight range instantly.
Calories
Calculate your BMR and TDEE using the Mifflin-St Jeor equation. Get personalized daily calorie targets for any goal.
TDEE
Calculate your Total Daily Energy Expenditure. The most important number for setting any nutrition goal.
Macros
Calculate your optimal protein, carbohydrate, and fat targets based on your calorie goal and fitness objective.
Calorie Deficit
Calculate your daily calorie deficit to lose weight at a safe, sustainable rate without sacrificing muscle.
Weight Loss
Calculate how long it will take to reach your goal weight, your required daily calorie deficit, and your projected weekly fat loss rate.
Muscle Gain
Calculate your optimal calorie surplus for lean muscle gain, your natural muscle-building potential, and required protein intake.
Daily Calories
Find out exactly how many calories you need per day to lose weight, maintain, or build muscle — personalised to your stats and activity level.
Guided Journeys
Connected step-by-step plans — not just isolated calculators.
All Free Tools
40+ calculators, planners, and quizzes — no sign-up needed.