Free Health and Fitness Calculators
Ten free online health calculators using established clinical formulas. BMI, TDEE, daily calories, macro split, ideal weight, body fat, sleep cycles, water intake, exact age, and pregnancy due date, all in your browser, no account required.
BMI Calculator
Calculate your Body Mass Index with metric or imperial units.
TDEE Calculator
Calculate your Total Daily Energy Expenditure.
Calorie Calculator
Calculate your daily calorie needs for any fitness goal.
Macro Calculator
Calculate your daily protein, carbs, and fat targets.
Ideal Weight Calculator
Find your healthy weight range using four established formulas.
Body Fat Percentage Calculator
Estimate body fat percentage using the US Navy method.
Sleep Cycle Calculator
Find the ideal bedtime or wake-up time by sleep cycle.
Water Intake Calculator
Calculate your daily hydration target based on weight and activity.
Age Calculator
Calculate your exact age in years, months, weeks, and days.
Pregnancy Due Date Calculator
Calculate your estimated due date from your last menstrual period.
10
Health calculators
kg/lb
Metric & imperial
Mifflin-St Jeor
TDEE formula
0
Data stored
WHO BMI classification (adults)
Same thresholds apply regardless of sex or age
| Category | BMI Range (kg/m²) | Health Risk |
|---|---|---|
Underweight | < 18.5 | Low weight-related risk; nutritional concerns |
Normal | 18.5–24.9 | Lowest associated health risk |
Overweight | 25.0–29.9 | Moderate risk of type 2 diabetes, hypertension |
Obese I | 30.0–34.9 | High risk across multiple chronic conditions |
Obese II | 35.0–39.9 | Very high risk; medical intervention advised |
Obese III | ≥ 40.0 | Severely high risk; clinical obesity |
Fitness calculators: body composition, nutrition, and wellness
The health calculators on this page cover the key measurements used in body composition assessment, nutrition planning, and general wellness tracking. The BMI calculator, body fat calculator, and ideal weight calculator help you understand where your current weight sits relative to established health ranges. The TDEE, calorie, and macro calculators provide nutritional targets for any fitness goal, weight loss, maintenance, or muscle gain.
The sleep cycle calculator, water intake calculator, age calculator, and pregnancy due date calculator cover the remaining health and wellness calculations most commonly needed. All calculators use established clinical formulas (Mifflin-St Jeor for TDEE, US Navy circumference method for body fat) and are estimates, not a substitute for professional medical advice.
Frequently asked questions
Yes. All 10 health and fitness calculators on ToolCenterHub are completely free to use with no account, no signup, and no usage limits. Results are calculated in your browser and nothing is stored.
The calculators use established formulas, Mifflin-St Jeor for TDEE and calories, the US Navy circumference method for body fat, and Devine, Robinson, Miller, and Hamwi formulas for ideal weight. These are the same formulas used in clinical and research settings. Results are estimates and should not replace advice from a qualified healthcare professional.
Yes. All calculators that accept weight and height measurements, BMI, TDEE, calorie, macro, ideal weight, and body fat, support both metric (kg, cm) and imperial (lb, ft/in) inputs. Switch between units using the toggle at the top of each tool.
Yes. The calculators provide estimates based on population-level formulas and are intended for general information purposes. Before making significant changes to your diet, exercise routine, or health practices, especially if you have any medical condition, consult a qualified healthcare professional.