Health & Fitness
BMI
BMI = kg / m²
Body mass index from weight and height — quick body-mass screening.
Calculate →BMR
BMR (Mifflin-St Jeor)
Basal metabolic rate from weight, height, age, and sex via the Mifflin-St Jeor equation.
Calculate →Body Fat Percentage
BF% (Navy / skinfold)
Body fat percentage from circumference (Navy method) or skinfold measurements.
Calculate →Calorie
kcal = BMR · activity factor
Daily calorie needs from BMR, activity level, and weight-management goal.
Calculate →Calories Burned by Activity
kcal = METs · weight · time
Calories burned per activity from MET value, body weight, and duration.
Calculate →Heart Rate
HR = 60 / R-R interval
Heart rate and heart-rate reserve from beats per minute or R-R intervals.
Calculate →Max Heart Rate
MHR = 220 − age (or Tanaka)
Maximum heart rate via age-prediction equations — Fox, Tanaka, Inbar, Londeree.
Calculate →Karvonen Heart Rate
HR_target = HRR · % + HR_rest
Target heart-rate zones using heart-rate reserve — the Karvonen formula.
Calculate →Target Heart Rate Zones
Zones at 50–100% of MHR
Five training zones from light recovery to maximum effort.
Calculate →Ideal Weight
IBW (Devine / Robinson / Miller / Hamwi)
Ideal body weight from height and sex via four classical formulas.
Calculate →Lean Body Mass
LBM = weight × (1 − BF%)
Lean body mass from total weight and body-fat percentage.
Calculate →Macro
P / C / F grams from kcal
Protein, carbohydrate, and fat targets from daily calorie intake and macro split.
Calculate →One-Rep Max (1RM)
1RM = w · (1 + reps / 30)
Projected one-rep max from a submaximal lift via the Epley formula and variants.
Calculate →Pregnancy Due Date
Due = LMP + 280 days
Estimated delivery date from last menstrual period — Naegele's rule.
Calculate →Running Pace
pace = time / distance
Race pace, finish time, and splits for any distance.
Calculate →Sleep Cycle
bedtime = wake − 7.5h (5 × 90 min)
Optimal sleep and wake times in 90-minute REM cycles.
Calculate →TDEE
TDEE = BMR × activity factor
Total daily energy expenditure from BMR and activity multiplier.
Calculate →Weight Loss Equations
Days = (kg × 7700) / daily deficit
Weight-loss timeline from daily calorie deficit and target weight change.
Calculate →Health and fitness calculators for body composition (BMI, body fat, ideal weight, lean body mass), metabolism (BMR via Mifflin-St Jeor, TDEE), heart rate (max heart rate, Karvonen target zones, resting heart rate), strength (one-rep max), endurance (running pace, calories burned), nutrition (macro splits, calorie intake), and recovery (sleep cycle, pregnancy due date).
Formulas follow established sports-science and nutrition references (Mifflin-St Jeor, Karvonen, Tanaka, Epley).
When to use these calculators
Use BMI for a quick body-mass screen, BMR + TDEE for daily calorie targets, and Body Fat % for composition tracking that BMI can miss. Use Max Heart Rate (Tanaka or 220-age) and Karvonen Heart Rate to set training zones for cardio. Use One-Rep Max (Epley formula) to project a max lift from a submax set. Use Macros and Calorie to plan a cut, bulk, or recomp.
These are educational tools — consult your physician before starting a new diet or training program, especially with any medical condition.
Frequently Asked Questions
- Which BMR formula is most accurate?
- Mifflin-St Jeor (1990) is the current gold-standard prediction equation, more accurate than the older Harris-Benedict for modern populations. The BMR calculator uses Mifflin-St Jeor by default; the Calorie calculator builds on it for TDEE estimates.
- How do Karvonen heart rate zones differ from straight max-heart-rate zones?
- Karvonen formula uses heart-rate reserve (max HR − resting HR) rather than max HR alone, which better individualizes target zones to fitness level. A trained athlete with low resting HR gets a wider absolute zone range than someone of the same age with a higher resting HR. The Karvonen Heart Rate calculator implements this.
- Is body fat percentage more useful than BMI?
- Yes — for individuals. BMI doesn't distinguish muscle mass from fat mass and misclassifies athletes as overweight. Body fat percentage (via the Body Fat calculator's Navy / skinfold methods) gives a composition-aware metric. BMI remains useful for population-level screening.