Free Fitness Calculators
Science-backed calculators for every fitness goal. No account, no ads, no guesswork — instant results based on validated research equations.
TDEE Calculator
Calculate your Total Daily Energy Expenditure — the complete picture of calories you burn including exercise, daily movement, and digestion.
Calorie Calculator
Find your daily calorie target for weight loss, maintenance, or muscle gain based on your age, sex, height, weight, and activity level.
BMI Calculator
Calculate your Body Mass Index and see how your weight compares to WHO health ranges. Includes limitations for athletes and muscular individuals.
Macro Calculator
Get personalised protein, carbohydrate, and fat targets in grams per day. Based on your goal — fat loss, maintenance, or lean bulking.
Body Fat Calculator
Estimate body fat percentage using the US Navy circumference method — more accurate than BMI for athletes. Requires only a tape measure.
Water Intake Calculator
Find your daily hydration target adjusted for body weight, activity level, and climate. Based on EFSA and WHO hydration guidelines.
Coming Soon
More tools in development, each targeting a specific training need.
1-Rep Max Calculator
Predict your 1RM from sub-maximal lifts using Epley, Brzycki, and Lander equations.
Heart Rate Zone Calculator
Find your Zone 1–5 heart rate ranges for optimal aerobic, threshold, and VO2 max training.
Ideal Body Weight Calculator
Calculate ideal body weight using Devine, Hamwi, and Robinson formulas with lean mass context.
Why use fitness calculators?
Most people underestimate or overestimate their calorie needs by 20–30%. A single week of accurate tracking — using your actual TDEE and macro targets — typically produces better results than months of guesswork. Fitness calculators remove the guesswork by anchoring your targets to validated scientific equations used in research settings.
The equations behind each calculator — Mifflin-St Jeor for energy expenditure, the US Navy method for body composition, EFSA guidelines for hydration — are the same ones used by registered dietitians, sports nutritionists, and clinical researchers. The difference is that they're now available instantly, free, and without booking an appointment.
Which calculator should you start with?
The order matters. Start with TDEE to establish your energy baseline — this number anchors every other calculation. Once you know how many calories you burn each day, use the Macro Calculator to split those calories into protein, carbs, and fat targets that align with your specific goal.
If you want a body composition check rather than calorie focus, start with the Body Fat Calculator. It gives you a more accurate picture of your physique than BMI — especially if you're training regularly. Use BMI as a secondary context metric, and track Water Intake separately since hydration affects performance and perceived hunger independently of calories.
How accurate are online fitness calculators?
Population-based equations have an inherent margin of error of ±5–10% because individual metabolic rates vary due to genetics, hormones, gut microbiome composition, and muscle fibre type. The Mifflin-St Jeor equation — used in the TDEE and Calorie calculators — is the most accurate predictive equation available for the general population, with a mean error of approximately 70 kcal/day compared to measured resting metabolic rate.
The practical approach: use the calculator result as your starting point, not a fixed rule. Track food and bodyweight for two weeks. If weight is moving in the wrong direction (or not moving when it should be), adjust calories by 100–150 kcal increments. This feedback loop — calculator estimate + real-world data — produces accurate, personalised numbers within 3–4 weeks.
The science behind the equations
| Calculator | Equation Used | Validated Accuracy |
|---|---|---|
| Calorie / TDEE | Mifflin-St Jeor (1990) | ±70 kcal/day vs measured RMR |
| Body Fat % | US Navy Circumference | ±3–4% vs DEXA scan |
| BMI | Quetelet Index (WHO) | Population-level health proxy |
| Macros | ISSN / Helms et al. guidelines | Evidence-based per-goal ranges |
| Water Intake | EFSA / WHO reference values | Adjusted for weight & activity |
Frequently Asked Questions
Are all the calculators completely free?
Yes — every calculator on Calorie Fit is free with no account required. All calculations happen in your browser. No data is stored or shared.
What's the difference between TDEE and the Calorie Calculator?
The TDEE Calculator gives you a detailed breakdown of all energy expenditure components (BMR, NEAT, TEF, exercise) and shows you calorie targets across five goals. The Calorie Calculator focuses on a quick, single-goal calorie target. Use TDEE if you want to understand the science; use Calorie Calculator if you want a quick number.
Do I need to use metric or imperial units?
All calculators support both metric (kg/cm) and imperial (lbs/inches) units. Simply select your preferred unit system before entering your data.
How often should I recalculate?
Recalculate every 4–6 weeks, or whenever your weight changes by more than 3–4 kg. As you lose or gain weight, your TDEE and calorie targets shift. Most people experience "plateaus" because they forget to recalculate after significant weight changes.
Go deeper with the science
Calculators give you the numbers. Our articles explain the science behind them — from TDEE components to protein timing to the truth about BMI.
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