Why Does My Oven Run Too Hot Or Cold?

Why is it that 350 degrees Fahrenheit in one oven never seems to be as hot—or as cold—in an oven across town? Or that the cooking time for your signature lasagna, which you've gotten down to a downright science in your own home, balloons when prepared in an Airbnb kitchen?

Simply put, it's because the number on an oven's blinking display is a lie. In 2015, Cook's Illustrated did a test of various ovens set to the same display temperature and found that their actual temperatures varied by as much as 50 degrees. That's a major problem when you're trying to follow a recipe, figure out timing before hosting a dinner party or otherwise maintain your sanity. 

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Here's the issue: The location of an oven's internal thermometer, which is responsible for that display number, is "necessarily in an out-of-the-way spot in the back, front, or side of the oven box," according to Cook's Illustrated. It registers the temperature of only that location, and that reading can vary fairly wildly from the temperature at the center of an oven, where cooking actually happens. 

Pretending we can exactly calibrate an oven's temperature is a fairly new thing. There's a reason that old-timey recipes are vague; for most of human history, it was virtually impossible to tell the exact temperature of a heating mechanism. According to Slate, oven manufacturers first added low, medium and high settings in the 1920s. Around the end of World War II, temperature dials got hash marks in 10-to-25-degree increments. Fast-forward to today, when ovens can be set to a desired temperature in five-degree increments. 

So what's a beleaguered home cook to do? "An oven is an insulated box with a fire in it—there's only so much control you can have over that setup, and we might as well be honest about it," Slate posits. You might want to invest in a good oven thermometer, too. Looking at the in-stock recommendations on Reviewed.com, we  suggest going with the Taylor large dial oven thermometer or the Farberware Protek classic oven thermometer, two options with a high degree of accuracy for a good value. 

If all else fails, check to see if your oven is calibrated correctly. If it's way off, time to call in an expert. Or, you know, make a salad instead.

Rachel Tepper Paley is a writer, editor , and sometimes illustrator living in New York City. See what she's eating over at @thepumpernickel on Instagram.