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Ice Basin — Cold Exposure · Tested COLD WATER.
CLEAR THINKING.

Ice Bath Ice Amount Calculator

ICEBASIN PLANNING TOOL / PHYSICS ESTIMATE

Estimate the ice before you buy the bags.

Enter the water you actually plan to use—not the tub's advertised capacity. The calculator balances the heat removed from that water against ice warming, melting, and the meltwater warming to your target.

Planning boundary: This is a physics estimate, not immersion guidance or medical advice. Real tubs vary with tub thermal mass, ambient conditions, body heat, insulation, mixing, ice temperature, melting, thermometer error, chiller use, and water replacement. Follow your tub manufacturer's guidance and ask an appropriate medical professional whether cold exposure is suitable for you.

Measurement system
Use filled water volume before adding ice.
A calculation input—not a recommendation.
0°F (−17.8°C) is a practical home-freezer default.
Adds contingency; it does not model a specific tub.

THE METHOD / NO BLACK BOX

What the estimate includes

  1. Cool the starting water: Qwater = mwater × cwater × (Tstart − Ttarget).
  2. Warm the ice to 0°C: Qice = mice × cice × (0 − Tice).
  3. Melt the ice: Qmelt = mice × Lfusion.
  4. Warm the meltwater: Qmeltwater = mice × cwater × Ttarget.
  5. Balance energy: the heat removed from the water equals the ice mass multiplied by the heat absorbed per kilogram of ice. The selected margin is applied after the ideal result.

The model uses 0.997 kg/L for water density, 4.186 kJ/(kg·K) for liquid-water specific heat, 2.108 kJ/(kg·K) for ice specific heat, and 333.55 kJ/kg for ice's latent heat of fusion. One U.S. gallon is 3.785411784 L and one kilogram is 2.20462262 lb.

Assumption: all entered ice starts at or below 0°C, fully melts, the mixture reaches one uniform final temperature at or above 0°C, and no other object or heat source participates. That is why a real-world margin and a thermometer matter.

Constants and sources

Constants are rounded to practical engineering precision; calculator arithmetic retains full internal precision and rounds displayed ice upward.

Plan the rest of your setup

After estimating your ice purchase, review these setup and maintenance guides. The calculator estimates heat balance only; its inputs and results do not establish a safe immersion temperature, duration, or personal suitability.