Free Cooking Time Conversion calculator with clear step-by-step results.
Cooking rates follow a temperature coefficient: each 10 C rise roughly doubles the rate of the chemical changes involved. Raising the doubling factor to the power of the temperature change divided by ten gives the rate ratio, and dividing the original time by it gives the new time.
Rate ratio
Ratio = Q10 ^ ((new temp - old temp) / 10)
Adjusted time
New time = original time / rate ratio
It is reliable for braises, slow roasts and custards where heat penetration governs. It works poorly for anything driven by surface browning or leavening, such as puff pastry or souffles.
Two is the standard assumption for cooking chemistry. Enzyme-driven and starch-gelatinisation steps sit nearer 1.5-2.5, so stay in that band unless you have measured otherwise.