Is BMI an accurate measure of health?

BMI compares weight with height. It is quick, but it cannot tell muscle from fat or show where weight is carried. Treat it as a rough screen, and combine it with other measures such as waist-to-hip ratio or body-fat percentage and with advice from a clinician.

How are daily calorie needs calculated?

The calorie calculator estimates your basal metabolic rate with the Mifflin-St Jeor equation, then multiplies it by an activity factor to give your total daily energy expenditure (TDEE). It is an estimate. Real needs vary with muscle mass and daily movement, so adjust after a few weeks of tracking your actual weight.

Can I use these results to make medical decisions?

No. They are informational. If a result worries you, such as a high blood-pressure category or a very low BMI, speak to a doctor. For pregnancy, a clinician's dating is the one to rely on.

How accurate are the ovulation and due-date estimates?

Both assume a typical cycle. Ovulation timing varies from cycle to cycle, so the fertile window is an estimate and not a guarantee. A due date worked out from your last period or a conception date is normally replaced by the date your clinician sets after a scan.

Do I have to enter private details, and are they kept?

You type measurements into your own browser. They are not sent to Stax or stored, and there is no account. Approximate numbers are fine for a rough answer.

Free Health

Health calculators turn a few measurements into a number you can reason about: body mass index, daily calories, protein and carbohydrate targets, body fat, how much water to drink, when to go to bed to wake between sleep cycles, or where your heart-rate training zones lie. They use published formulas (the Mifflin-St Jeor equation for calorie needs, the US Navy method for body fat, the Karvonen formula for heart-rate zones), and each page names the one it uses.

They are screening and planning aids, not diagnoses. A BMI or a blood-pressure category is a starting point for a conversation with a doctor or a dietitian, not a verdict. Pregnancy and ovulation dates are estimates based on a typical cycle. The Love Calculator is just for fun.

18 tools available

Most Popular

BMI Calculator

Calculate Body Mass Index with metric or imperial units.

Try it free →Calorie Calculator

Calculate BMR, TDEE, and daily calorie needs using the Mifflin-St Jeor equation.

Try it free →Body Fat Calculator

Calculate body fat percentage using the US Navy formula or BMI-based method. Shows lean mass, fat mass, and category.

Try it free →

Which tool should I use?

Weight in relation to height: BMI Calculator — metric or imperial units; a quick screen, not a diagnosis.
How many calories you burn in a day: Calorie Calculator — BMR and TDEE from the Mifflin-St Jeor equation.
Daily protein, carbs and fat: Macro Calculator — targets for cutting, maintaining or bulking, built on your calorie figure.
Body fat percentage: Body Fat Calculator — US Navy or BMI-based method, with lean and fat mass.
Fat distribution: Waist-to-Hip Ratio Calculator — waist-to-hip and waist-to-height ratios with a risk category.
How much water to drink: Water Intake Calculator — uses body weight, activity and climate.
When to sleep or wake: Sleep Calculator — counts back in 90-minute sleep cycles.
A blood pressure reading: Blood Pressure Checker — classifies it against AHA categories and logs readings.
Training for a run: Pace Calculator — pace, finish time or distance, with splits; the heart rate zone calculator sets your training zones.
Energy burned in a workout: Calories Burned Calculator — MET values for more than 40 activities.
A due date or fertile window: Pregnancy Due Date Calculator — from last period, conception date or IVF transfer; the ovulation calculator covers the fertile window.
Exact age: Age Calculator — years, months and days, with a countdown to the next birthday.

All Health (18)

BMI Calculator

Calculate Body Mass Index with metric or imperial units.

Open tool →Age Calculator

Calculate exact age in years, months, days with next birthday countdown.

Open tool →Calorie Calculator

Calculate BMR, TDEE, and daily calorie needs using the Mifflin-St Jeor equation.

Open tool →Ideal Weight Calculator

Calculate ideal body weight using Devine, Robinson, Miller, and Hamwi formulas.

Open tool →Sleep Calculator

Find ideal bedtime or wake-up time based on 90-minute sleep cycles.

Open tool →Pace Calculator

Calculate running pace, finish time, or distance. Shows km/mile splits for any race distance.

Open tool →BSA Calculator

Calculate Body Surface Area using Mosteller, Du Bois, Haycock, and Boyd formulas.

Open tool →Waist-to-Hip Ratio Calculator

Calculate WHR and WHtR with cardiovascular risk assessment per WHO guidelines.

Open tool →Water Intake Calculator

Calculate daily water intake based on body weight, activity level, and climate with a personalised hydration schedule.

Open tool →Body Fat Calculator

Calculate body fat percentage using the US Navy formula or BMI-based method. Shows lean mass, fat mass, and category.

Open tool →Pomodoro Timer

Online Pomodoro timer with customisable focus, short break, and long break durations. Tracks sessions and total focus time.

Open tool →Pregnancy Due Date Calculator

Calculate estimated due date from LMP, conception date, or IVF transfer. Shows weeks pregnant, trimester, and milestones.

Open tool →Macro Calculator

Calculate daily protein, carbs, and fat targets based on your BMR, TDEE, and fitness goal (cut, maintain, or bulk).

Open tool →Ovulation Calculator

Calculate ovulation date and fertile window from last period and cycle length. Shows cycle calendar and 3-cycle forecast.

Open tool →Blood Pressure Checker

Check blood pressure readings against AHA guidelines. Classify as Normal, Elevated, or Hypertensive and log readings over time.

Open tool →Calories Burned Calculator

Calculate calories burned using MET values for 40+ activities. Supports metric and imperial with activity comparison.

Open tool →Heart Rate Zone Calculator

Calculate 5 heart rate training zones using the Karvonen formula or % of max HR. Includes fat burn, aerobic, and max effort zones.

Open tool →Love Calculator

Fun love compatibility calculator. Enter two names and get a compatibility percentage score. Just for entertainment! 💕

Open tool →

Frequently Asked Questions

Is BMI an accurate measure of health?: BMI compares weight with height. It is quick, but it cannot tell muscle from fat or show where weight is carried. Treat it as a rough screen, and combine it with other measures such as waist-to-hip ratio or body-fat percentage and with advice from a clinician.
How are daily calorie needs calculated?: The calorie calculator estimates your basal metabolic rate with the Mifflin-St Jeor equation, then multiplies it by an activity factor to give your total daily energy expenditure (TDEE). It is an estimate. Real needs vary with muscle mass and daily movement, so adjust after a few weeks of tracking your actual weight.
Can I use these results to make medical decisions?: No. They are informational. If a result worries you, such as a high blood-pressure category or a very low BMI, speak to a doctor. For pregnancy, a clinician's dating is the one to rely on.
How accurate are the ovulation and due-date estimates?: Both assume a typical cycle. Ovulation timing varies from cycle to cycle, so the fertile window is an estimate and not a guarantee. A due date worked out from your last period or a conception date is normally replaced by the date your clinician sets after a scan.
Do I have to enter private details, and are they kept?: You type measurements into your own browser. They are not sent to Stax or stored, and there is no account. Approximate numbers are fine for a rough answer.