What formula does this use?

It uses Newton's law of cooling: T(t) = Tw + (T0 − Tw) × e^(−k·t), where Tw is groundwater temperature, T0 is starting wort temperature, and k is a rate constant for the chiller type and volume. Solving for t gives the cooling time.

Why can't water cool wort below groundwater temperature?

A chiller can only approach the temperature of the coolant flowing through it. If your groundwater is 20°C you cannot reach 15°C with that water alone — you would need an ice or glycol pre-chiller. The tool flags an impossible target.

Why are counterflow and plate chillers faster than immersion?

Immersion chillers cool a whole kettle of wort by conduction and convection around a coil. Counterflow and plate chillers cool wort in a thin stream as it passes through, giving a much larger temperature gradient and a higher effective rate constant.

How accurate is the estimate?

It is an approximation. Real cooling depends on coil surface area, water flow rate, whether you stir or recirculate, and kettle geometry. Use it to plan brew-day timing, not as an exact stopwatch figure.

Is my data uploaded anywhere?

No. The estimate is computed entirely in your browser and nothing is sent to a server.

Wort Chiller Cooling Time Estimator

The Wort Chiller Cooling Time Estimator predicts how long it will take to bring boiling wort down to pitching temperature with your chiller. Knowing this lets you time the rest of brew day — sanitising the fermenter, preparing yeast — so nothing waits on a kettle that is still too hot.

How it works

Cooling follows Newton’s law of cooling: the rate of temperature drop is proportional to the difference between the wort and the coolant. Mathematically:

T(t) = Tw + (T0 − Tw) × e^(−k·t)

where T0 is the starting wort temperature, Tw is the incoming groundwater temperature, t is time in minutes, and k is a rate constant that depends on the chiller type and the wort volume.

Solving for the time to reach a target temperature Tt:

t = −(1 / k) × ln( (Tt − Tw) / (T0 − Tw) )

Larger volumes lower the effective k (more thermal mass per unit of cooling surface), so the constant is scaled by volume. Immersion chillers use a smaller base constant than counterflow or plate chillers, which cool a thin stream of wort with a much larger temperature gradient.

Temperature limits

A chiller can never cool wort below the temperature of the water running through it. If your target is at or below the groundwater temperature, the estimator reports that the target is unreachable with that coolant and you would need an ice bath, pre-chiller, or glycol loop.

Example and notes

Chilling 23 L (about 6 gal) of 100°C wort to 20°C with 15°C groundwater on an immersion coil typically lands in the 20–30 minute range, while a plate or counterflow chiller can do it in a fraction of that as wort passes through. The figure is a planning estimate — stirring the wort, increasing water flow, and using a pre-chiller all shorten the real time.