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Tools
Free tools for sleep and hair
Explore caffeine timing, sleep shortfall, bedtime planning and hair length with clear calculations and editable assumptions.
Caffeine half-life calculator
Estimate caffeine remaining at bedtime from several drinks. Adjust the half-life, view the curve and compare moving every drink two hours earlier.
Open toolSleep debt calculator
Compare recorded sleep with your own nightly target. See each night's shortfall, the total and average, with missing nights excluded from the calculation.
Open toolBedtime and wake-up calculator
Work backwards from your wake time. Add your sleep target, time to fall asleep and optional wind-down to build a clear bedtime plan without cycle predictions.
Open toolHair growth calculator
Estimate months to your target hair length in centimetres or inches. Change the assumed growth rate, include trims and see a simple length timeline.
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