Health Calculators
Every health calculator on the site, in one place — body composition, nutrition, fitness, and reproductive health tools, grouped by what you're actually trying to figure out.
Each tool below shows its formula directly on the page, so you can see exactly how your result was reached instead of taking a number on faith. Everything runs in your browser — nothing you enter is ever sent to a server or saved. Jump to a section, or scroll through all 21.
Weight & body composition
Understanding your body's numbers beyond the bathroom scale.
- BMI Calculator — the standard height-to-weight screening measure, with its healthy range and limitations explained.
- Body Fat Calculator — estimates body fat percentage from tape measurements, using the US Navy method.
- Lean Body Mass Calculator — everything on your body except fat, estimated from height and weight.
- Waist-to-Hip Ratio Calculator — a simple measurement some health organizations use alongside BMI.
- Ideal Weight Calculator — a rough reference range, shown alongside why it isn't a personal target.
- Body Surface Area Calculator — a measurement sometimes referenced in clinical contexts.
Energy & nutrition
How many calories you burn, and how to split them.
- BMR Calculator — the calories your body burns at complete rest, using the Mifflin-St Jeor equation.
- Calorie Calculator — your estimated daily maintenance calories, based on activity level.
- TDEE Calculator — the same core calculation, with more detailed training-volume options.
- Macro Calculator — splits a daily calorie target into grams of protein, carbs, and fat.
- Protein Intake Calculator — a daily protein gram target based on body weight and activity level.
- Calories Burned Calculator — estimates calories burned during a specific activity using MET values.
Fitness & training
Tools for planning and pacing workouts.
- Target Heart Rate Calculator — estimated maximum heart rate and common training zones by age.
- One-Rep Max Calculator — estimates your maximum lift from a weight and rep count you've already done.
- Pace Calculator — your running pace, plus projected times for common race distances.
- Water Intake Calculator — a daily hydration target based on body weight and exercise.
Reproductive health
Cycle tracking and pregnancy planning tools.
- Pregnancy Due Date Calculator — estimates your due date from your last period or conception date.
- Ovulation Calculator — an estimated fertile window based on your cycle.
- Period Calculator — predicts your next few period start dates.
- Pregnancy Weight Gain Calculator — recommended total weight gain ranges based on pre-pregnancy BMI.
Safety & awareness
Educational tools with a strong safety framing.
- Blood Alcohol Calculator — an educational BAC estimate. Never used to judge whether it's safe to drive.
Frequently asked questions
Are these health calculators free to use?
Yes — all 21 tools on this page are free, with no account or sign-up required.
Do these calculators give medical advice?
No. Each tool applies a standard, published formula for informational and planning purposes. For any medical decision, talk to a doctor or other qualified healthcare professional who knows your full health picture.
Is any of the information I enter saved or shared?
No. Every calculation runs directly in your browser — nothing you type, including any health details, is sent to a server or saved anywhere.
Which calculator should I start with?
Start with what you're actually trying to find out — the section headings above group tools by topic, whether that's body composition, daily calorie needs, workout planning, or cycle tracking.
Looking for a different category? Browse all calculators on the homepage. For articles and updates about these tools, see all Health Calculators posts.