What Your Oven Isn’t Telling You

by Angela (Oh She Glows) on April 5, 2012

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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.

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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.

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[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.

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I squinted my eyes really hard (am I getting old or are those things just really tiny?)

To me, it looks about 315-320F:

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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.

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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.

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Have you ever measured your oven’s true temperature or calibrated your oven? I bet you sure are curious now…

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{ 19 comments… read them below or add one }

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JessE @ LoveLifeFromScratch April 9, 2012 at 11:39 am

Another aspect to think about is the heating and cooling cycle of the oven. As the heating coil turns on and off the temp fluctuates. My gem of an oven fluctuates +-50 degrees!

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Angela (Oh She Glows) April 9, 2012 at 12:22 pm

yea I have realized mine fluctuates too…made muffins the other day and it went from 330 to 360 I think

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ashley rebekah April 12, 2012 at 2:33 pm

because of all the somewhat-shady-yet-beautifully-artsy apartments i’ve managed to dwell in, i consider my oven thermometer my go-to kitchen tool! each apartment got lovelier and lovelier, while each oven got scarier and scarier (and older).

i’ve actually ever had an oven that was spot on with what the dial said, so i always spend the first few days in my new place figuring out just how ‘off’ the oven is, then making a little index card of the proper temps for the oven and slapping i up on the stove or wall directly above the stove. works like a charm ;)

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Elizabeth April 12, 2012 at 9:42 pm

I should definitely get an oven thermometer!

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Ian the Barbarian April 13, 2012 at 6:19 am

I agree – you have to get to know your oven. Apart from the temperature settings, there are hot & cold spots in most ovens.

If you think that’s bad, check out your measuring jugs.
It’s easiest in grammes/litres – one litre of water weighs 1000 grammes.

Measure out a litre and weigh it – I guarantee it will be way out!

Think of the mess it makes of your recipes!

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Dave April 15, 2012 at 12:09 pm

I had an oven that was far off and had a repairman come in. He found that the oven temp prob had caked/baked on food and when he cleaned it off it worked perfectly.

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MJI January 16, 2013 at 1:16 pm

I recently moved into an apartment. The stove is from like the 1970’s. As soon as I started using the oven I noticed something odd. No matter what temp I set it at, it always got hot and smoky inside. The light near the dial would even turn off as if it had hit a max temperature and tripped a safety shut off. I tried to bake something at 250 and saw my oven temp go out of my thermometer range. I guess 400 is it’s max it records. I didn’t know how to fix the oven, so I went ahead and called to have it repaired. I’m waiting for a replacement part.

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Sarah January 25, 2013 at 8:55 am

You’re lucky! I’ve got a Belling and the oven temperature is all over the place. I’ve been told that 20 degrees out either way is acceptable. Today I was told 30 degrees out is fine and to buy a proper thermometer to use. It measures different temperatures in all parts of the oven and today was only close to what it should be in the top back right-hand corner. Basically if set to 180 degrees there’s no way of knowing whether it’s cooking at 180 or 200 or 160, or anywhere in between. Following the manufacturer’s instructions to reduce the temperature as it’s a fan oven means potentially expecting something to cook while the oven is only 140 degrees. Seems there’s nothing I can do to improve things and any cooking will be pure luck if it comes out cooked properly.

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Katie Randall February 10, 2013 at 12:25 pm

OMG I was just telling my husband that my oven is off by more than 50 degrees and he said no way that I had to be wrong…thank you so much for this, I am def getting a thermometer today no more burned stuff for this house!!

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Angelica July 15, 2013 at 8:30 pm

I just recently moved out on my own for the first time. I’m not exactly an expert at baking, but I like to do it here and there as a hobby. Today I burnt my first batch of cookies ever. (At the same time they were horribly undercooked on top.) I did the same thing, and got a thermometer and checked things out. Turns out when I set the dial to 350 it actually went up to 450-460 inside the oven. I tired again and set it at 250 instead, but strangely it still went up to about 400. Hrm. Contacted the manager and landlord about this oven for the 3rd time. The first time we only had one working burner and the second time the oven didn’t even lite.

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Mollie September 25, 2013 at 1:47 pm

I just moved into a new apartment and testing my oven temp was the first thing I did. It’s an older oven so I knew it may be off. After preheating to 350, I checked the oven thermometer and “bam!” It was closer to 450! My oven reads almost 100 degrees over! I did this test a few times, using a few different thermometers with the same sad results. I bake and cook a lot so this is a huge disappointment :(
I’d recommend everyone invest in an oven thermometer. Since I’ve been using it, everything taste so much better. No lie, it’s one of the best (kitchen) investments I’ve ever made. What a difference! Thanks for the post about this issue. It’s more important than people think!

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Tenessa April 19, 2014 at 11:03 pm

Thank you so much for this blog. I use my oven all the time when preparing dinner for my family. We just moved and I soon as I was cooking my first meal I realized my oven wasn’t working like my previous oven. It took so much longer to cook. A meal that normally took 30 minutes ended up taking 50 minutes in this oven. I put up with in for about a 2 month now, but now that I’m trying some new recipes for Easter I figured I better attempt to find a fix so that I don’t under or over cook anything or end up spending more time cooking then necessary. This was a huge help. I went out and purchase a thermometer and sure enough my oven was off by 15F I was only getting to 335 when I set it to 350. I made the adjustments and now my oven is heating up to the correct degrees. Thank you again!!!

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Jenny November 30, 2014 at 1:36 am

The oven in our new house is no more than 2 yrs old.
I felt it was very hot but thought it was because it was a fan oven
And set it lower temperature. But I think that it’s waay too hot still.
A sandwich cake turned out like very laarge biscuits.
The idea of baking white bread slices is very good and I must get an
Oven thermometer!

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Luis May 24, 2015 at 12:04 pm

I was curious too. My thermostat says 270, but my over is set to 300! also, the oven is new. Bummer.

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Gloria October 20, 2015 at 12:43 pm

How do u calibrate ur oven temperature?

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Jerry Wides October 28, 2015 at 8:09 am

Digital readout on a GE gas oven, doesn’t go any higher than 290. It is a dial thermostat.

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jan November 23, 2015 at 5:23 pm

Thank you for this information! I just got a new Whirlpool range and after several experiences of undercooked frozen dinners, I decided to test it at various temperatures, preheating from 20 minutes to an hour. It’s always at least 50-75 degrees lower than it should be. Had the repairman out today and he said nothing’s wrong with it, tests ok, and that the oven thermometers don’t work with the newer ovens. Give me a break. I can guarantee you nothing’s wrong with the oven thermometer. Looking forward to calibrating the oven with your instructions and see if I can get it much closer to the temperature I’ve selected.

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Patti November 20, 2016 at 1:24 pm

Looks like the same make as my brand new oven that is out over 75 degrees and has a non workingm convection. Lol mi even did the same and thought it was a defective Cdn Tire oven thermometer. Wish I had my old coil topmstobr back.

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Sandy Tugnum January 28, 2017 at 4:13 pm

Have an Whirlpool Accu-Bake gas range. After a couple baking disasters and trying not to blame the tool used a digital thermometer.

Observations: When the oven indicates it is up to preheat temperature, it is not. The variation is at least + / – 15 degrees F. So on preheat when the read out indicates the oven is at 350 degrees F it is 335 degrees F. At times the variation is much as +/- 25 degrees F. So a set point of 365 degrees F yields an average oven temperature of about 350 degrees F.

So DON’T put your baking in when the oven indicates it is up to baking temperature. It will spend most, if not all its baking time at least 15 degrees under the set point. That doesn’t take into account the temperature loss when loading the oven.

There must be an oven out there that has a variable rate gas valve to reduce the significant variation +/- of set point! It’s like a car with an off on switch in place of an accelerator pedal. Hard on the souffles….!

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