Health Calculators

Calculate your Body Mass Index (BMI) and understand your weight category.

Estimate your maximum heart rate and see your five training zones in bpm, using the percentage-of-HRmax or the Karvonen heart-rate-reserve method.

Turn a daily calorie target into grams of protein, carbohydrate and fat with a diet preset or a custom split.

Calculate your basal metabolic rate in kcal and kJ with the Mifflin-St Jeor, Harris-Benedict, Katch-McArdle and Schofield equations.

Calculate your daily calorie target from your goal and pace, with the projected change over time and a macro split.

Estimate your total daily energy expenditure, read the calories each activity level implies, and see the goal band around maintenance.

Estimate your body-fat percentage from tape measurements with the U.S. Navy method, or from BMI when you have no tape.

Estimate a child’s adult height from both parents’ heights, or read a child’s height against the CDC growth reference at their age.

Find the best time to wake up or go to bed using sleep cycle science.

Calculate your sleep window using sleep restriction therapy (SRT) and CBT-I principles.

Calculate your total sleep debt and find out how long recovery takes.

Find your chronotype and estimate social jet lag based on your sleep schedule.

Plan your sleep schedule for time zone travel and reduce jet lag.

Find age-based sleep recommendations for children and teenagers.

Calculate your ideal weight with the Devine, Robinson, Miller, Hamwi, Peterson and Broca formulas, and see the healthy weight range for your height.

Estimate your lean body mass and fat mass from your weight and body-fat percentage, read the fat-free mass index against reference values, and compare the Boer, James and Hume estimates.

Estimate your one-rep max from a weight and the reps you lifted, with Epley, Brzycki and Lombardi side by side.

Work out running or cycling pace, time or distance from the other two values.

Check the U.S. Army waist-to-height standard and see the superseded 2023 tape estimate.

See how much of a caffeine dose is left in the body at bedtime, the latest time you can have it and stay at or below the level you choose, and the hour it falls to that level.

Work out how long to nap and when to wake: a power nap, or one to three full sleep cycles of about 90 minutes each.

Learn what Cognitive Behavioral Therapy for Insomnia (CBT-I) is, its core components, and why it is the first-line treatment for chronic insomnia.

How sleep restriction therapy works for insomnia: time in bed, sleep efficiency, fixed wake time, safety floors, and weekly adjustments.

How to track your sleep with a sleep diary and calculate sleep efficiency for CBT-I sleep restriction therapy.

How stimulus control therapy strengthens the bed-sleep connection and helps treat chronic insomnia.

The difference between sleep compression and sleep restriction therapy, and when a gradual approach may be more appropriate.

Why CBT-I is more effective than sleep hygiene alone for chronic insomnia, and how both approaches differ.

Cognitive restructuring techniques from CBT-I: managing worry time, catastrophic thoughts, and sleep performance anxiety.

Medical and safety considerations before trying sleep restriction therapy: bipolar disorder, seizure risk, sleep apnea, and other contraindications.

How to adjust your sleep window each week based on sleep efficiency during CBT-I sleep restriction therapy.

How sleep diary, stimulus control, sleep restriction, cognitive techniques, and relaxation fit into a structured CBT-I program.

Learn how sleep debt works, how to estimate your shortfall, and how to recover with gradual pacing.

Understand chronotypes, circadian rhythm, social jet lag, and how schedule alignment affects sleep quality.

Plan your sleep for time zone travel with light exposure guidelines and gradual schedule shifts.

Age-based sleep recommendations for children and teens, including naps and individual variation.

Understand the sleep cycle, REM and deep sleep stages, and how cycle timing affects sleep quality.

How daily light timing works around your own clock, and where melatonin fits as the body's dark signal.