Health calculators

Enter up to three caffeine doses and when you took them. The calculator estimates how much caffeine is still active at bedtime, how much carries into waking, and when an additional dose would need to stop.

Enter your body size, activity level, goal weight, and planned calorie intake to estimate the deficit and the date your goal would be reached if the pace stayed linear.

Enter the four Durnin-Womersley skinfold measurements to estimate body density and body fat. The calculator also reverses the selected conversion equation to show the four-site sum corresponding to a target estimate.

Measure your body, desk, keyboard, chair, and monitor to work out practical changes for a fixed-height workstation. The results give tape-measure starting points for the chair, footrest, keyboard, and screen rather than a generic height recommendation.

Enter adult weight, sodium values, a TBW profile, replacement fluid, replacement time, and ongoing free-water loss. The calculator estimates the deficit, fluid-equivalent volume, starting hourly rate, and modeled first-day sodium change.

Enter the blood-volume method, body size, and starting and minimum acceptable hematocrit or hemoglobin. The result compares the Gross dilution-corrected estimate with the simpler conservative formula.

Enter the delivered protein and 24-hour urinary urea nitrogen to estimate nitrogen balance. The calculator also reverse-solves the protein intake needed to reach a selected target balance.

Enter same-draw chemistry values to compare the standard osmolal gap, an ethanol-adjusted gap, the Khajuria-Krahn equation, and albumin-corrected anion gap in one place.

Enter up to seven nights of time in bed, time to fall asleep, and other awake time. The calculator summarizes the diary without setting a sleep schedule or recommending a bedtime.

Enter your usual sleep onset and wake times for workdays and free days. The calculator shows your midsleep shift, social jetlag, weekly average sleep, and the sleep-corrected free-day midsleep used as an MCTQ-style chronotype estimate.