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About this tool
Build an hourly drinking schedule for dry air-conditioned workspaces, with caffeine and insensible water loss accounted for.
The Air-Conditioned Office Hydration Planner converts your working hours, room temperature, humidity and caffeine intake into a timed drinking schedule with a millilitre figure for each reminder. It separates the two things air conditioning actually does: it raises respiratory and transepidermal water loss slightly, both computed here against a reference 22 °C / 40% RH room, and it removes the environmental cues that normally prompt you to drink. ASHRAE Standard 55 puts comfortable indoor humidity at 30-60%, and most conditioned offices run below that.
Open Air-Conditioned Office Hydration Planner on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Reports the real extra loss from dry air — usually tens of millilitres, not litres — instead of inflating it.
Produces timed reminders rounded to 25 ml sips, plus a refill count for your own bottle or mug.
Applies diuresis only above the 300 mg dose where research finds a net effect, and flags the 400 mg daily EFSA limit.
Only mildly. Dropping a room from 40% to 25% relative humidity typically adds a few tens of millilitres of water loss across a full working day through breathing and the skin — far less than one extra glass. The dry-eye and dry-throat feeling is real, but it comes from surface evaporation on the eyes and airway, not from whole-body dehydration.
For most adults the whole-day drinking target is roughly 28 ml per kg of body weight once water from food is subtracted, so about 2 litres for a 70 kg person. A nine-hour working day covers a little over half your waking hours, which usually puts the desk share near 1.1-1.3 litres — the calculator splits it for your own weight and hours.
Yes, at ordinary doses. Reviews of caffeine and fluid balance find no meaningful net diuresis in habitual consumers below about 300 mg of caffeine a day — roughly three cups of filter coffee — so those drinks count as fluid. Above that, expect a modest extra urine output, and EFSA puts the safe daily ceiling for healthy non-pregnant adults at 400 mg.
ASHRAE Standard 55 recommends indoor relative humidity between 30% and 60%. Below 30% people report dry eyes, dry throat, static and irritated contact lenses; above 60% the room feels muggy and mould risk rises. A small desk humidifier or plants raise local humidity more effectively than drinking extra water does.