Cold Plunge Chiller Size Calculator
Enter your tub, temperatures, environment and plumbing. The calculator checks cooling load, cooldown range and real pump flow together.
How to use the chiller size result
Start with the actual water volume, not only the tub's advertised outside size. Choose the insulation and cover that most closely match the installed tub, then use the hottest ambient condition you realistically expect. For outdoor systems, sun exposure matters because direct solar load can overwhelm a setup that looks adequate in shade.
For plumbing, enter the full hose or pipe length through the complete loop and count restrictive fittings conservatively. The calculator compares the pump curve with pipe, fitting, filter and chiller resistance to estimate the operating flow that remains after system losses. That value is checked against the chiller's published minimum-flow requirement.
Why the result is a range
Cold-plunge equipment is not tested under one universal standard. Insulation quality, solar exposure, filter condition and low-water-temperature chiller capacity can vary. ChillSizer therefore reports ranges and confidence levels rather than pretending a DIY system will cool in an exact number of minutes.
Run your expected setup first, then rerun a conservative summer case. If the recommendation becomes marginal, improve insulation or plumbing, increase flow margin, or choose the next suitable chiller class before buying equipment.
What to read next
Use the complete system guide for the design sequence, the plumbing diagram for component order and service valves, and the methodology for the assumptions behind thermal and hydraulic calculations.
What the calculator does not claim
It does not predict medical outcomes, sanitation performance, electrical-code compliance or exact manufacturer warranty suitability. Where product pressure-drop or low-temperature capacity data are incomplete, the engine uses bounded uncertainty and downgrades confidence rather than pretending the value is exact.