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…
I have never measured my oven’s true temperature because its brand new…. but now I’m curious!
I never even thought about this before. I had no idea they could be so far off!
I notice the new apartment oven seems much hotter. I’m also going from gas to electric. I miss my gas burners, but I like the electric oven. I’ve got to get myself a new thermometer (or 2) so see what is going on in there though!
Wow this is SO informative. I need to test my oven like this. I’ve done tests to see where there are hot patches: lay white bread on a cookie sheet, like 8 slices and put it in at like 350F. My oven toasts the left half of the bread on the cookie sheet far more quickly and more intensity than on the right hand side. I could literally burn a pan of brownies on one side of the pan and keep them raw on the other, if I don’t rotate halfway thru. SUCH a pain….and this is a “nice” oven, that’s about 3 year old. Renting, don’t own, so I’m at the mercy.
I love this experiment you did and I will be doing my own now, too! Because if my 350F isn’t everyone else’s and vice versa, that is a huuuuuuge variable. Far more so than I’d say mis-measuring flour by 1/2 cup so to speak.
That is another great test (about the bread slices) I will have to try that one out sometime.
I never even thought about this! I have actually gotten some emails from readers that have done a recipe of mine…and it was over cooked. I will be doing this asap!
Thanks for the great reminder!
I’ve wondered about my oven temperature, but haven’t checked it myself. I have a gas stove so I’m not sure if I would be able to calibrate it, but I definitely want to get a thermometer so I can check it out! Thanks for the info!
Yes, after way too long using it and wondering why it took SO long for things to cook in it! It’s about 10degrees too cool. It’s gas and I don’t have the manual so I just set it ten degrees warmer and wait a few more minutes after it tells me it’s come to temp. It seems to take a 3-5 more minutes to actually get there. It’s amazing what a difference just those 10degrees has made!
So funny! I did this recently. Ever since we moved into our rental, I knew that the oven was hotter than it says it was. I burned tray after tray of cookies, leaving the insides raw. I estimated that it was about 50 degrees hotter than indicated. Finally, after getting so frustrated when trying to bake, I went out an bought an oven thermometer. Turns out my oven is approximately 75-80 degrees hotter than it says!!! I was appalled, but relieved to know that it wasn’t my cooking skills. Wish I could say I went the extra step to try to fix the oven, but I’m lazy and just turn the oven to about 260 now when I need to bake.
hah well that works too!
My oven is only about 4 1/2 years old and I use an oven thermometer every time. The only frustration I have is that my oven thermometer seems incredibly slow and my oven beeps about 15 minutes before my thermometer measures the desired temp. That could either mean that the oven is beeping prematurely or that the thermometer is slow to register.
I had the gas company come out to calibrate the oven a couple years ago and he said it was right on, but really it runs about 5* cool.
That’s a great point about the thermometer maybe being slow…it’s something we thought might be possible too!
Our first oven in this apartment was really, really old. It had a metal handle that got about as hot as the inside of the oven and a knob to set the temperature. Of course, all of the markings were rubbed off of the knob, so I had to get an oven thermometer and spend a LOT of time figuring out the oven temperature and where to mark the knob. Of course, the oven door didn’t have glass so I had do keep opening the oven door, thus giving poor readings. Our new oven is much nicer, but it didn’t take too many batches of dry muffins and burnt sweet potato fries to find that its fancy digital thermometer was a dirty dirty liar. I didn’t do quite as impressive or well-designed of a research project as you though – I just set the oven 15 degrees lower and it hasn’t failed me yet.
lol @ dirty dirty liar.
That is so funny that you posted this today! We just moved about a week ago and so I am getting use to a new oven at higher altitude. I made a new to me dairy/egg free french toast this morning and had my burner in between medium and low and it totally burned! I have to cook everything on low now! Blargh!
I better try your test out on my oven before I make your pizza recipe tonight!
I’ve had vegan french toast burn on me too
Ah that is so annoying! I remember having serious oven troubles when we had an electric stove and convection oven. We recently switched over to a gas stove and convection over and luckily the newer version is working much better!
I’m so impressed that you took the time and effort to do this (and made it look easy!). I’ve suspected for some time that my oven–very old, not even digital!–lies to me. It never crossed my mind to take a thermometer and verify, but now i’ll definitely be checking into the situation…
Oooh interesting. I never knew that was the case!
Lol I LOVE that you replicated your experiment by going out to buy another thermometer. I’ve never checked my oven before but I know I should. I think mine gets too hot.
Great experiment! I need to test my oven now.
You did the test so scientifically even with TWO thermometers! Now I’m wondering how my oven reads..
My oven actually IS super-old. The oven thermometer is my only way of knowing what temperature I have set it to. The dial doesn’t even have marks! It may have at some point, but as far as we can tell, the kitchen was built in the 1920s, and the oven came in maybe as late as the 1950s, probably earlier. So any marks that may have once existed have been rubbed into oblivion. It’s adorable, but it took some getting used to.
I bet it did! It must have a ton of character though..would be cool to look at if anything.
After moving into our rental from a house with a brand new oven to a house that is far more dated, I bought an oven thermometer to see what the temperature was reading since this oven has a dial and is hard to tell what you are really setting it at. Ends up I have to wait an extra 10 minutes after it says the oven is preheated to get the correct temp…no big deal, just helpful to know :) Smart to do from time to time. I actually keep my thermometer in the oven and always place it at the same level of whatever it is I’m baking to ensure that it is at the right temp….
yea that’s exactly what I’ve been doing too. Peace of mind :)
Wow – that is some serious kitchen commitment! I’d never thought to test the oven!
I do feel like my b-f’s gas oven is much better for baking than my electric oven. I love cooking with gas!