Health Calculators
About These Health Calculators
These free health calculators help you understand your body's numbers — from whether your weight falls in a healthy range to how many calories you need each day to reach your goals, how much water to drink, and what heart rate zones to train in. All calculators support both imperial (lbs, feet/inches) and metric (kg, cm) units.
All calculators run entirely in your browser. Nothing you enter is sent to a server or stored anywhere.
Tools in This Category
- BMI Calculator — Calculate your Body Mass Index, see your weight category, and find your healthy weight range for your height.
- Body Fat Percentage Calculator — Estimate your body fat percentage using the U.S. Navy circumference method with just a tape measure. See your lean mass, fat mass, and fitness category.
- Ideal Weight Calculator — Run four proven medical formulas (Hamwi, Devine, Robinson, Miller) to find the ideal weight range for your height and sex.
- TDEE Calculator — Calculate your Total Daily Energy Expenditure and get daily calorie targets for weight loss, maintenance, or muscle gain.
- Macronutrient Calculator — Split your daily calorie target into protein, carbohydrate, and fat grams based on your goal and diet preference (balanced, low-carb, keto, high-protein, or low-fat).
- Water Intake Calculator — Get a personalized daily hydration target in ounces, cups, liters, and bottles based on your weight, activity level, and climate.
- Heart Rate Zone Calculator — Find your five heart rate training zones for fat burn, cardio, threshold, and peak. Supports the standard, Tanaka, and Karvonen formulas.
- Due Date Calculator — Estimate your pregnancy due date and key milestones from your last menstrual period or conception date.
Important Disclaimer
These calculators are informational tools based on widely used formulas (such as the Mifflin-St Jeor equation for BMR, the standard WHO BMI categories, and the U.S. Navy body fat method). They are not a substitute for advice from a qualified healthcare provider. Individual results vary based on factors these formulas cannot account for, including medical conditions, medications, body composition, and activity patterns.
How to Use These Calculators Together
Each calculator answers a specific question, and they're most powerful when used together as a system:
- Start with BMI and Body Fat. BMI gives you a quick weight-to-height snapshot; body fat percentage tells you what that weight is actually made of. Athletes often have a high BMI but healthy body fat.
- Find a realistic target. The Ideal Weight Calculator gives you a science-based range — not a single number — to aim for based on four clinical formulas.
- Calculate your energy needs. The TDEE Calculator tells you exactly how many calories you burn per day. This is the foundation of any effective nutrition plan.
- Break calories into macros. The Macronutrient Calculator splits your calorie target into daily protein, carb, and fat targets matched to your goal and dietary preference.
- Optimize your training. The Heart Rate Zone Calculator ensures your workouts are at the right intensity — whether you're building aerobic base in Zone 2 or pushing VO₂ max in Zone 5.
- Stay hydrated. The Water Intake Calculator gives you a daily fluid target adjusted for your body weight, activity, and climate.
How to Use These Calculators
Each calculator is designed to answer one specific question. For best results:
- Use accurate, current measurements — weigh yourself in the morning before eating for the most consistent results.
- For body fat measurements, use a flexible tape measure and follow the measurement instructions exactly — small errors in technique can shift the result by 1–2%.
- Choose the activity multiplier honestly for TDEE — most people are more sedentary than they think.
- Use the results as a starting point, track your actual progress over 2–3 weeks, and adjust from real-world data rather than solely from calculated estimates.