Free online health & fitness calculators
Ten instant health calculators that run entirely in your browser. No signup, no upload, no ads.
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BMR Calculator (Mifflin)
Calculate your Basal Metabolic Rate and daily calorie needs using the Mifflin-St Jeor equation.
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Body Fat Calculator
Estimate body fat percentage using the US Navy measurement method.
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Ideal Weight Calculator
Find your ideal body weight range using Devine, Robinson, Miller, and Hamwi formulas.
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Water Intake Calculator
Calculate your recommended daily water intake based on weight and activity level.
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Pregnancy Due Date
Calculate your estimated due date from your last menstrual period using Naegele's rule.
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Ovulation Calculator
Estimate your ovulation date and fertile window based on your last period and cycle length.
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Heart Rate Zones
Calculate your five cardio training heart rate zones from your age and resting heart rate.
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Sleep Cycle Calculator
Find the best bedtime or wake time to complete full 90-minute sleep cycles.
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Calorie Burn — Walking
Estimate calories burned walking based on your weight, pace, and duration.
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Macro Split Calculator
Break daily calories into protein, carbs, and fat grams for your fitness goal.
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Why use browser-based health calculators?
Every calculator here runs entirely inside your browser — no server round trips, no account needed. Results are instant and your personal health data never leaves your device. These tools cover the most common health and fitness calculations for anyone tracking nutrition, fitness, or reproductive health.