Health Calculators
Track your health metrics with our BMI calculator, age calculator, and date-based tools. Free, instant results with no registration.
Health calculators use units and guidance relevant for United Kingdom. BMI, age, and date tools adapt to local conventions.
Health Calculators
BMI Calculator
Calculate your Body Mass Index (BMI) and understand your weight category.
Sleep Calculator
Find the best time to wake up or go to bed using sleep cycle science.
Sleep Restriction Therapy Calculator
Calculate your sleep window using sleep restriction therapy (SRT) and CBT-I principles.
Sleep Debt Calculator
Calculate your total sleep debt and find out how long recovery takes.
Chronotype Calculator
Find your chronotype and estimate social jet lag based on your sleep schedule.
Jet Lag Calculator
Plan your sleep schedule for time zone travel and reduce jet lag.
Kids Sleep Calculator
Find age-based sleep recommendations for children and teenagers.
What Is CBT-I?
Learn what Cognitive Behavioral Therapy for Insomnia (CBT-I) is, its core components, and why it is the first-line treatment for chronic insomnia.
Sleep Restriction Therapy Explained
How sleep restriction therapy works for insomnia: time in bed, sleep efficiency, fixed wake time, safety floors, and weekly adjustments.
Sleep Diary and Sleep Efficiency
How to track your sleep with a sleep diary and calculate sleep efficiency for CBT-I sleep restriction therapy.
Stimulus Control Therapy
How stimulus control therapy strengthens the bed-sleep connection and helps treat chronic insomnia.
Sleep Compression vs Sleep Restriction
The difference between sleep compression and sleep restriction therapy, and when a gradual approach may be more appropriate.
CBT-I vs Sleep Hygiene
Why CBT-I is more effective than sleep hygiene alone for chronic insomnia, and how both approaches differ.
Cognitive Techniques for Insomnia
Cognitive restructuring techniques from CBT-I: managing worry time, catastrophic thoughts, and sleep performance anxiety.
When Sleep Restriction May Not Be Appropriate
Medical and safety considerations before trying sleep restriction therapy: bipolar disorder, seizure risk, sleep apnea, and other contraindications.
How to Adjust Your Sleep Window Week by Week
How to adjust your sleep window each week based on sleep efficiency during CBT-I sleep restriction therapy.
CBT-I Plan: How the Pieces Fit Together
How sleep diary, stimulus control, sleep restriction, cognitive techniques, and relaxation fit into a structured CBT-I program.
Sleep Debt Recovery
Learn how sleep debt works, how to estimate your shortfall, and how to recover with gradual pacing.
Chronotype and Circadian Rhythm
Understand chronotypes, circadian rhythm, social jet lag, and how schedule alignment affects sleep quality.
Jet Lag Sleep Planning
Plan your sleep for time zone travel with light exposure guidelines and gradual schedule shifts.
Kids Sleep Needs by Age
Age-based sleep recommendations for children and teens, including naps and individual variation.
Sleep Cycles and Stages
Understand the sleep cycle, REM and deep sleep stages, and how cycle timing affects sleep quality.