Calibrating Your Oven Without a Thermometer

Calibrating Your Oven

I’m currently taking a free online lecture seminar at Harvard on the science of cooking and I’ve decided to blog the labs, as they’re very educational in and of themselves. The first week we calibrate our ovens by using the melting point of sugar, which is 366°F.  This enables us to find out how hot/cold our oven is running without using a thermometer, though I included one for comparison.

Start by preheating your oven to 340°F as above. Then take a ramekin or other heatproof dish and add 1/2 tablespoon of sugar to it (I used more for photographic purposes).


Place the ramekin in your oven at 340°F and wait 15 minutes. After 15 minutes, check to see if the sugar has melted.


Nope, not melted. Increase the temperature of your oven either 5° or 10°, depending on how accurate you want to be versus how much time you want to invest in this project. Put the ramekin back in the oven for 15 more minutes, and check again. Repeat until it melts.


My sugar melted at 350°F on the oven, which tells you that my oven is running at LEAST 16°F hot.  Therefore if I want to bake something at 350°F, I should enter in a temperature of around 335°F, not 350. If I want 375°F, I would use 355 or 360°F. If I cared to find out exactly how off it was, I would try perhaps 347°F and see if sugar melted, but I think I’m good with just using a 15° offset.

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  • Shelley @ Two Healthy Kitchens October 17, 2013, 6:56 am

    This is super-interesting! I’ve never heard of this technique, but it makes complete sense – what a great tip! I love your mad science approach to cooking – such a great adventure! Oh – and I can’t wait to check out the Harvard course! Thanks, Dustin!

    • Cooking Madly October 17, 2013, 8:43 am

      Thanks! I was surprised by the idea as well, but it makes sense. I’m really excited about this Harvard course as well, we’ll have to talk about what we both get from it once we’ve completed the first week or two.