Cold Plunge Protocol Timer
Most people guess a round number and bail when it hurts. Enter your water temperature to get a session length based on commonly cited cold-exposure protocols, then run an actual countdown timer for it. Nothing uploaded.
Recommended Protocol
Countdown Timer
Ready
Learn more: how this timer picks a session length
The four temperature bands
The tool holds four water-temperature bands and looks up whichever one your reading falls into. At 5°C and below the range is 30 to 90 seconds, flagged as advanced only. Above 5°C up to 10°C it is 1 to 3 minutes, above 10°C up to 15°C it is 3 to 5 minutes, and above 15°C up to 20°C it is 5 to 10 minutes.
Each band's upper edge belongs to that band. Exactly 10.0°C returns the 1 to 3 minute range, while 10.1°C moves you into the 3 to 5 minute one. That jump at a tenth of a degree comes from using fixed bands instead of a curve, so a reading near an edge is best read as sitting between the two ranges.
Where the countdown number comes from
The clock starts at the midpoint of whichever band is active, rounded to a whole second. For 8°C that is the middle of 60 and 180 seconds, so the display reads 02:00. At 12°C it reads 04:00, and at 18°C the midpoint of 300 and 600 seconds gives 07:30.
The midpoint is only a starting value. The target session length box takes anything from 10 to 1800 seconds, and a number typed there replaces the suggestion; Reset reloads the clock from whatever that box says. Edits to the box do nothing while the countdown is running, so pause it first.
Changing the water temperature while the clock is stopped or paused pulls in the new band's midpoint and overwrites your target. While the countdown is running it does not: the range and level above update, but the clock keeps counting the session you started.
Units, clamping, and the limits of the table
The °F toggle converts your entry back to Celsius before the lookup, so the bands sit at the same water temperatures either way, with edges at 41°F, 50°F, 59°F, and 68°F. Switching units rewrites the number in the box to one decimal place rather than clearing it.
Readings outside 0 to 20°C are clamped to the nearest end rather than extrapolated. Enter 25°C and you get the 5 to 10 minute mild band; enter -2°C and you get the 30 to 90 second one. Nothing here models water colder or warmer than those limits, so a clamped answer is the edge of the table rather than a figure for the temperature you typed.
The page does two things: it reads a fixed table and it runs a countdown. It has no input for your age, health, fitness, how acclimated you are, or how the water feels on the day, and cold water immersion carries real cardiovascular risk. Anyone with a heart condition or any other medical concern should talk to a doctor before using cold water immersion at all.
FAQ
Why do the colder bands allow less time?
The tool reads that relationship straight out of its fixed table; it calculates nothing from your body or your conditions. The coldest band tops out at 90 seconds while the mildest one starts at 300. Where the real limit sits for a given person is a medical question, and this tool does not answer it.
What happens if I enter water warmer than 20°C or below freezing?
The lookup clamps to the nearest defined band. 25°C is treated as 20°C and returns 5 to 10 minutes; -2°C is treated as 0°C and returns 30 to 90 seconds. There is no data past those two ends, so the answer stops changing there.
Can I run a session length the tool did not suggest?
Yes. The target session length box overrides the midpoint and accepts 10 to 1800 seconds, and Reset reloads the clock from whatever it says. The suggested midpoint only comes back when you change the water temperature while the clock is stopped or paused.