Water Cooling Calculator

Cool Hot Water for Tea and Drinks

Boiling water is too hot for many teas and instant drinks. This calculator estimates how long to wait, how much cold water to add, or how many pours between cups you need to reach a target temperature. Pair it with the Tea Brewing Calculator and the Chilled Drink Calculator for full drink planning.

Wait for Natural Cooling

Passive cooling uses Newton's law of cooling for an open cup at room temperature. Enter initial temperature, target temperature, room temperature, water volume, and cup diameter.

$$T(t) = T_a + (T_i - T_a) \cdot e^{-kt}$$

The tool solves for time when the water reaches your target. Larger cup surface area cools faster. More volume holds heat longer.

Add Cold Water

Mixing hot and cold water instantly hits your target. The volume of cold water needed depends on starting temperature, target temperature, and cold water temperature.

$$\text{cold ml} = \frac{V_{\text{hot}} \times (T_i - T_f)}{T_f - T_c}$$

Pour Between Cups

Pouring between two cups increases surface exposure and speeds cooling. The calculator estimates pours needed based on about 4°C drop per pour for quick cup-to-cup transfer.