How many bags of ice does it take to hit 50°F? Enter your tub size and starting water temperature to get the exact ice weight and estimated cost.
🧊 Calculate Your Ice Needs
The Physics of Cooling a Cold Plunge
Cooling water with ice is a straight heat-transfer problem: one pound of ice absorbs about 144 BTU of heat as it melts (its latent heat), plus a bit more as it warms to the final water temperature. A gallon of water weighs ~8.34 lb and holds ~1 BTU per pound per °F. That’s what this calculator uses — so a 75-gallon tub going from 65°F to 50°F needs roughly 50 lb of ice, at a cost of ~$8–15 depending on local ice prices. For a ready-made tub with a built-in chiller, check our best cold plunge tubs roundup instead.
Reference: Ice Requirement Lookup (75-gallon tub)
| Temp drop | Ice needed | Bags (10 lb) | Approx. cost |
|---|---|---|---|
| 5°F | ~26 lb | 3 | Check price |
| 10°F | ~52 lb | 5 | Check price |
| 15°F | ~78 lb | 8 | Check price |
| 20°F | ~104 lb | 11 | Check price |