According to a test by Cook’s Illustrated in 2011, different ovens set to the same temperature can vary by as much as 90 degrees.
Yes….90 degrees.
If you are an avid baker or cook (or even just an occasional one), this news should be a bit concerning. Or maybe this news is relief; you now have a valid excuse for why your sweet potato fries always burn! Or at least I do…
When we moved in, one of the first things I did was check the oven’s true temperature. It’s an older oven (edited to add: I don’t mean super old by the way. The oven in our last house was 30 yrs old and I doubt this one is more than 10 yrs, so technically, it’s newer to me) and I was concerned about switching to a new-to-me oven without checking things out first. It’s especially important to me because I post my recipes for all of you and I have to be as accurate as possible.
For some reason, I had a bad feeling about this oven, even though it’s quite nice on the eyes.
I set my oven to 350F and placed my oven thermometer (from Kitchen Stuff Plus) in the center of the oven on the middle rack. This would be the first of several tests I would end up doing.
[But it’s called a “TRUE TEMP”…what could possibly go wrong???]
The oven beeps when it has supposedly finished preheating, so I eagerly walked over to the oven when it alerted me. I didn’t want to impact the temperature by opening the door, so I quickly turned on the oven light and bent down to look at the temperature.
The oven temperature read about 290F or so. I can’t quite remember it exactly, but it wasn’t even close! I gave the oven the benefit of the doubt, assuming that it just took longer to preheat.
And I waited some more. The temperature climbed slowly and after a good 15 minutes, I decided it wasn’t moving anymore. I waited an extra 30 minutes just to be sure.
I squinted my eyes really hard (am I getting old or are those things just really tiny?)
To me, it looks about 315-320F:
This is about a 30-35 degree difference. I also tested various places in the oven (on the side and in the back), but they were all around that temperature give or take 5 degrees. I even left it in for a full hour just to be sure. Nada.
Every good researcher knows that it’s to never advisable to rely on a single study, right? So, I headed out and bought another brand of oven thermometer (this time from Canadian Tire) and tested it once again.
Replicate.
Wouldn’t you know it, the temperature was the exact same. Approximately 320 degrees Fahrenheit when it should have been 350. At least the thermometers are accurate. ;)
I Googled if there was any way to fix my wonky oven temperature and it turns out that it’s fairly easy to calibrate many kinds of ovens, depending on the severity.
Always start with the manual first. I looked for the owner’s manual, but wasn’t able to locate one (not surprising being in a rental and all). Eric suggested that we find the model number of our oven and see if we could find instructions online. He wasn’t able to find the manual online for this oven.
Eric finally ended up finding directions on Appliance 411- “How do I adjust the oven temperature on my range?”.
Following these directions, he was able to set the oven temperature higher (35F was as high as he could go), however it’s still not a perfect calibration. Now, when I set the oven to 350F, it heats to about 340F, so it’s still about 10 degrees too low. To attain 350F, I have to set the oven to 360F and also wait about 5-10 minutes after the oven tells me it’s preheated. This isn’t a huge deal, as long as I’m careful and I keep my oven thermometer in the oven when using.
The oven thermometer is probably the best solution we have right now, aside from actually paying someone to repair it (or asking the landlord), which I probably wouldn’t bother with unless it got worse.
Our first adventure in oven calibration is now complete.
One thing I love about this oven? The stove top heats up much faster than our old oven back at home. You win some, you lose some! I’ve burned a few veggie burgers so far, but I’ll get used to it eventually.
Have you ever measured your oven’s true temperature or calibrated your oven? I bet you sure are curious now…
Wow this is good to know! I was never a cook but I’m starting to cook and bake a lot more now so I should check my oven too..
That is so smart! Thanks for the tip!
Amazing the variance but it’s good to know these things! We have done the same thing and still have our trusty oven thermometer, although, a second tester is a good idea.
I’ll be honest…I am a gas snob. I cannot go back to electric after cooking for so long with gas! Oh my, it is so nice! Our beloved oven went on the blink and my husband fixed it the first time and the second problem required a repairman, who happened to be an absolute peach.
hah I hear that from so many people! Can’t wait to try them out some day.
Yes, ever since we moved the times I’ve had in my recipes were off by 5 to 10 min. With my first oven it was about 30 minutes off! Ah, the joys of renting with old appliances. After a few attempts I usually develop a feel for it (having a glass door with a light helps too)! I don’t know why I haven’t tried the thermometer.
Hahaa! My oven has been off by 150+ degrees for at least a year. We had our landlord fix it once (he put in a new thermostat), but it just goes back to its old habit after a while! My oven isn’t fancy or digital, so I have to use the old style dial to adjust the temperature. It’s frustrating!! I keep hoping the entire oven will die so we can have it replaced.
Oh my gosh I want to test our oven now!
Hi, I did the same tests, but for my “counter oven”… Why? Because I do polymer clay jewelry and the temperature needs to be to a tee (so it does not break after)… I even got another thermometer, like you, because I thought the first one was not working!! I’m sure many ovens have, to some extent, a temp variation… Maybe I should look into oven calibration too (didn’t know you could!). Thanks for the info (and making me laugh as it remninded my of all the tests I did too!).
You should really consider getting a bulb thermometer, rather than a spring thermometer (which is what you bought). There is a big difference in the range at which they are accurate. I noticed a big difference when I switched.
Because a spring thermometer relying on the expansion and contraction of two metals, and the metal springs can only expand and contract so much, the thermometer is only reliable within a range of degrees, which is not as large as the range at which your oven will run. A bulb thermometer relies on the physics of expanding liquid, which is not limited to the physical constraints that metals are, so it is much more accurate over a much wider range of temperatures.
If you have a probe thermometer, you can use that to calibrate your oven too, although it requires much more time and attention. I simply recorded the highest and lowest tempuratures of my oven (according to the probe thermometer) over a period of 30 minutes. I took the average tempurature, and adjusted my oven accordingly. The process also taught me that my oven cycles run about 10 minutes.
-Jon
loganskitchen.com
Thanks Jon, I’ll look into it!
Interesting! I’ve never measured my oven temperature, but I feel like I should – I know it’s wayyyy off from what it should be. It drove me crazy when I was still adjusting to it because I burnt so many things! :P
My parents got a new oven a couple years back and while I was living there, it was awesome! I’d bake all kinds of cakes, cookies and cupcakes and they turned out perfectly. Now that I’m in a rental condo, it’s a whole different story. First of all, I can’t convection bake anything, which is a HUGE bummer and I’m pretty sure our oven is heating up to a temp lower than is actually says, similar to yours. I have yet to get an oven thermometer to check but now that your post has reminded me, I think I will–especially with wedding season coming up and cupcakes on the horizon.
Wow, good experiment! My oven at my place is totally wacky and sometimes will take WAY longer to cook things than it’s supposed to. The temp is probably way off on it, but at least I know I’m not just imagining it now!
Baking in different ovens is insane – I now! I used to housesit a lot (I mean, a lot) and always had to adapt to cooking in different kitchens. I always use an oven thermometer, even now – and it would seem that slow preheating is a common problem! I always wait far past the time it says it’s ready.
Also, a tip: never leave your oven thermometer in the oven when using the ‘clean’ cycle. I did this once and opened the oven to find my thermometer completely dead – it literally was pale like a ghost, and it failed to work at all. Poor thermometer! RIP
ah that is a great tip and probably easy to overlook. Now I just need to clean this beast…that will be the next project.
Teaching my 9 year old to use the oven, he often looks at me like I’m nuts when I tell him, “see the recipe says 350 so I want you to preheat the oven to 365.” He’s starting to believe me when I show him the oven thermometer inside that is RIGHT ON once the preheat is done. Go Mom. Way to have cred.
love that. He’s probably like…how does she always know everything? heh
Hmmm, very interesting. This makes me want to check my oven, as I am sure it is off.
Oh my gosh!
So true, I never thought I could calibrate my oven!!
Similarly, I moved into a rental that as a VERY wonky oven and have had many frustrating expereinces with it taking a long time to cook something or over cooking it totally.
I am deffinately going to have to do some experimenting!!
Great tip!
ahhh but the problem with electric stove tops is the amount of time they take to cool down! i often found in my old flat that you couldn’t just turn off the heat and leave the pan on the top, because it would just carry on cookin! interesting post!
yea that is true…gotta be careful with them. Im constantly burning things
I have never done this before, but you are right — I am SO curious now! :-) Thinking I will be doing this on Saturday!
Such a beautiful research! Thank you!
I did this last year but of course never thought to blog about it! I found that mine was 20 or so degrees lower than what it should be and did the fancy preset you mentioned to get it up to a higher temp. Great post, Angela!