Ice Bath Chiller Size Calculator: What Size Do You Need?

A chiller lets you skip the daily bags of ice, but only if it can shift heat fast enough. Enter your tub volume, the water temperature you start from, the temperature you want, and how quickly you want to get there. The tool works out the cooling capacity your chiller needs. The number that matters on a chiller's spec sheet is its cooling capacity in watts or BTU/hr, not its horsepower label.

The maths is straightforward: cooling 1 litre of water by 1°C takes about 1.16 watt-hours of heat removal. The calculator adds a 30% margin so your chiller is not running flat out at 100% the whole time and can cope with heat creeping in from a warm garden. If your tub is uninsulated or sits in direct sun, treat that margin as a minimum.

A chiller pulls water down slowly and then holds it, so a smaller unit run overnight often does the job for less money than a big one. If you want the water cold within an hour, expect to size up sharply, or top up with a few bags of ice for the first plunge and let the chiller maintain it after that. Once you know the ice side of things too, the ice bath ice calculator works out how many bags you would otherwise need per session.