Health CalculatorsScience-Based Body & Nutrition Tools
Track body composition, set nutrition targets, plan weight loss, and monitor hydration with free health calculators backed by established clinical formulas.
Body Composition
Measure and understand your body — beyond the scale
BMI Calculator
Body Mass Index with Navy method body composition & healthy weight range by height.
Open calculatorBody Fat Calculator
Accurate body fat percentage via 7 measurement methods including Navy & skinfold.
Open calculatorIdeal Body Weight
Your healthy weight target using 4 clinical formulas: Devine, Hamwi, Robinson & Miller.
Open calculatorNutrition & Weight Management
Calories, macros, weight loss timelines & hydration
Calorie Calculator
Precise TDEE based on activity level, age & goal — with macro split and meal timing guidance.
Open calculatorMacro Calculator
Daily protein, carbs & fat targets for weight loss, muscle gain, keto, maintenance or any custom goal.
Open calculatorWeight Loss Calculator
Calorie deficit, daily intake target & realistic timeline to your goal weight.
Open calculatorWater Intake Calculator
Personalized daily hydration needs in oz/L based on body weight, activity level & climate.
Open calculatorPregnancy & Fertility
Cycle tracking, ovulation windows & due date planning
Health & Fitness Guides
Evidence-based articles with interactive calculators built in
Why BMI Is Misleading — And What Actually Measures Health
BMI puts everyone from elite athletes to sedentary adults in the same buckets. Here is what the number actually measures, where it fails, and what to track instead.
6 min readHow Many Calories Should You Eat? Your TDEE Explained
Counting calories only works if you know your actual target. Your TDEE — Total Daily Energy Expenditure — is the number that determines whether you gain, maintain, or lose weight. Here is how to find it.
7 min readWhy Body Fat % Tells You More Than BMI Ever Could
A 6'1" linebacker weighing 230 lbs has a BMI of 30.3 — clinically obese. His body fat is 8%. A 5'5" sedentary person weighing 160 lbs has a BMI of 26.6 — merely "overweight." Her body fat is 35%. BMI tells you weight relative to height. Body fat tells you what that weight is made of.
5 min readHow Fast Can You Safely Lose Weight? The Actual Science
One pound of fat is roughly 3,500 calories. To lose 1 lb/week, you need a 500 calorie/day deficit. Here's what that looks like in practice — and why most people plateau before they expect to.
5 min readMacro Calculator Guide: Setting Your Protein, Carbs, and Fat Targets
Counting calories is step one. Counting macros is step two — and it's where real results come from. Here's how to set your macro targets based on your goal.
6 min readHow Much Water Should You Actually Drink Per Day?
The "8 glasses a day" rule was never based on evidence. Your real hydration needs are specific to your body, activity level, and climate. Here is the science and how to calculate your actual target.
5 min readHow to Use Health Calculators Effectively
Health calculators provide clinically-derived estimates — not diagnoses. They use validated formulas like the Mifflin-St Jeor equation for calorie needs, the Devine formula for ideal body weight, and the Navy tape method for body fat estimation. The goal is to give you a reliable starting point, not a medical verdict.
For weight management, start with the Calorie Calculator to find your TDEE (Total Daily Energy Expenditure), then use the Macro Calculator to set protein, carb, and fat targets aligned with your specific goal. The Weight Loss Calculator then shows a realistic timeline so you can set a sustainable deficit without losing muscle.
For body composition, BMI is a starting point but has well-known limitations — it doesn't distinguish between fat and muscle. The Body Fat Calculator using the Navy method gives a more accurate picture of body composition, and the Ideal Body Weight Calculator provides a clinically-based target range rather than a single number.
All health calculators on this site are free, require no account, and don't store any personal data. Results are for informational purposes — always consult a licensed healthcare provider for medical advice.