# Nothing "accurate" about calibrating an oven's temperature! Arrrgg! **URL:** \ **Category:** Factual Questions\ **Created:** [March 29, 2016, 3:43pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531 "2016-03-29T15:43:36Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [March 29, 2016, 3:43pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/1 "2016-03-29T15:43:36Z")
I bought a new (used) electric kitchen range. 1970’s model for $50 from [Craigslist.org](http://Craigslist.org). So I decided to “calibrate” the oven for when I set it to 350 degrees F., the oven heats to that temperature… Well my cheap oven thermometer said the oven was 300 degrees. And a digital meat thermometer said the oven was 370 degrees! Note the oven temperature can be adjusted up/down by removing the oven temperature knob and turning a small screw in the hollow shaft or by loosening screws on the back of the knob - moving dial. Instructions here… [Appliance411 FAQ: Oven Temperature Calibration](http://www.appliance411.com/faq/temperature-calibration.shtml) BUT!!! It sure helps if I am using an accurate thermometer. Where can I get one? And for that matter, I need to open the door to read the oven thermometer - can’t read it through the window. An accurate oven thermometer with a “bulb” and line which could be mounted outside of the oven - say sensor mounted inside the oven, then line ran out the back. Gauge mounted on wall in back of oven. That would be great! Even better would be the above, but one which also reads up to 1000 degrees F. (for self cleaning mode which goes up to around 860 degrees F. on my model). ---
**Author:** ![araminty](https://avatars.discourse-cdn.com/v4/letter/a/b5e925/32.png) [@araminty](https://boards.straightdope.com/u/araminty)\ **Post date:** [March 29, 2016, 3:50pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/2 "2016-03-29T15:50:42Z")
You mean a probe thermometer? They’re everywhere. Try [amazon](http://smile.amazon.com/CDN-DTP482-Programmable-Probe-Thermometer/dp/B00046YFHE?sa-no-redirect=1). ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [March 29, 2016, 4:00pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/3 "2016-03-29T16:00:14Z")
“A man with two thermometers never knows how hot it is.” ---
**Author:** ![core](https://avatars.discourse-cdn.com/v4/letter/c/d26b3c/32.png) [@core](https://boards.straightdope.com/u/core)\ **Post date:** [March 29, 2016, 4:01pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/4 "2016-03-29T16:01:51Z")
Rather than buying a probe thermometer (which would only get used once in my house), I’d pick up a cheap infrared gun thermometer. Because those are handy for tons of other things around the house too. No, they won’t read through glass, but it only takes a couple seconds to open the door and shoot the back wall or a mass you have placed on the rack. Keep in mind the thermostat may let the temperature fluctuate wildly between cycles unlike say your HVAC thermostat, so take the readings at the same points in the cycle each time. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 29, 2016, 5:06pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/5 "2016-03-29T17:06:37Z")
> [@Just\_Asking\_Questions](#): > > “A man with two thermometers never knows how hot it is.” Sure he can. He just averages the values. That’s okay, right? (I say this having just read a report about thermal measurements on a heat shield in which all measurements were averaged into a single value to show that the temperature is just below the threshold…which means that there were several measurements in locations that were above the threshold temperature, and therefore the shield doesn’t meet design critiera.) The thermometers may not be at fault; depending on the construction (where the heating elements are located, how well the oven permits natural convection) the temperature may vary considerably from location to location. The most accurate way to evaluate this is with a calibrated [infrared thermometer](http://www.omega.com/googlebase/product.html?pn=OS425-LS&gclid=CMf-5NOv5ssCFRSPfgodYN0FTQ), but a cheap way to do this is just to put a small ovensafe container of a measured amount of water in different locations in the oven and time how long it takes to boil off, then calculate the heat flux. Back in the days when commercial ovens were still using radiant heating, a good cook or baker had to know which areas of the oven heated up to what temperature and where to best put different goods to get the correct result. These days with modern convection ovens with direct impingement flows, the heating is so consistent throughout the oven that location is rarely a significant problem; you get the same time and temperature in the back and on the sides as front and center. Stranger ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [March 29, 2016, 5:42pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/6 "2016-03-29T17:42:48Z")
My sister used to have an oven with the dials just labelled with the numbers from 1 through 10 with no “real temperature” calibration. Apparently the oven was made by a company that also sold baking ingredients and recipe books that would just use the numbers instead of temperatures, and then that company went out of business. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 29, 2016, 6:01pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/7 "2016-03-29T18:01:58Z")
I recently calibrated my MIL’s oven, using a Thermocouple-input thermometer. I found that before calibration, it had a consistent 25°F offset above 300°F, and after calibration, it was almost prefect. The low-temperture settings were inaccurate both before and after. I took readings every 50°F from 200 - 450, and considered the temperature stable once the oven had gone through 2 on/off heating element cycles at each setpoint. I also noted the high/low switch points, which were around 25°F. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 29, 2016, 6:09pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/8 "2016-03-29T18:09:13Z")
> [@Stranger\_On\_A\_Train](#): > > Sure he can. He just averages the values. That’s okay, right? I believe this is a reference to an [old sailor’s adage](https://en.wikipedia.org/wiki/History_of_longitude#Lunars_or_chronometers.3F): “When going to sea, take one chronometer or three.” ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [March 29, 2016, 6:15pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/9 "2016-03-29T18:15:23Z")
> [@leahcim](#): > > My sister used to have an oven with the dials just labelled with the numbers from 1 through 10 with no “real temperature” calibration. Apparently the oven was made by a company that also sold baking ingredients and recipe books that would just use the numbers instead of temperatures, and then that company went out of business. I was under the impression that this used to be very common in England. You would see recipes with gas setting 7 or similar for setting the oven temperature. > **[Gas mark](https://en.wikipedia.org/wiki/Gas_Mark)** > > The gas mark is a temperature scale used on gas ovens and cookers in the United Kingdom, Ireland and some Commonwealth of Nations countries. > The draft 2003 edition of the Oxford English Dictionary lists the earliest known usage of the concept as being in L. Chatterton's book Modern Cookery published in 1943: "Afternoon tea scones… Time: 20 minutes. Temperature: Gas, Regulo Mark 7". "Regulo" was a type of gas regulator used by a manufacturer of cookers; however, the scale has now become universa... ---
**Author:** ![mmmiiikkkeee](https://avatars.discourse-cdn.com/v4/letter/m/edb3f5/32.png) [@mmmiiikkkeee](https://boards.straightdope.com/u/mmmiiikkkeee)\ **Post date:** [March 29, 2016, 7:06pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/10 "2016-03-29T19:06:44Z")
[Thermoworks](http://www.thermoworks.com/?gclid=CJG8mNHI5ssCFYhffgodeUoC-A) is a US company that makes or sells all kinds of modern (and decent quality) thermometers suitable for calibrating an oven. I’d go with the type shown above, with a probe you can leave in the oven or food. You can get wireless ones that you can even check with your smartphone; those ones will actually plot of graph of the temp changes so you can get crazy-accurate calibration results if you really want to. And these actually do have multiple uses… even the $60 one I bought (chef alarm) has a range of -50C to several hundred +… meaning you could use it as an indoor/outdoor thermometer (in addition to using it to monitor big pieces of food cooking without having to take it in and out to check with a hand probe). But yes, a 1970s $50 electric oven will have cheap-ass temp controls as well as hold and cold spots. And a cheap oven thermometer won’t be much better when trying to calibrate it. I highly recommend getting at least 1 modern food thermometer… I recently bought all 3 types (hand probe, IR gun, and leave-in probe), and find them very useful. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [March 29, 2016, 7:18pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/11 "2016-03-29T19:18:49Z")
> [@gazpacho](#): > > I was under the impression that this used to be very common in England. You would see recipes with gas setting 7 or similar for setting the oven temperature. > > [Gas mark - Wikipedia](https://en.wikipedia.org/wiki/Gas_Mark) It could have been related to that usage, but this oven was electric. ---
**Author:** ![WotNot](https://avatars.discourse-cdn.com/v4/letter/w/e19b73/32.png) [@WotNot](https://boards.straightdope.com/u/WotNot)\ **Post date:** [March 29, 2016, 7:21pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/12 "2016-03-29T19:21:23Z")
> [@gazpacho](#): > > I was under the impression that this used to be very common in England. You would see recipes with gas setting 7 or similar for setting the oven temperature. > > [Gas mark - Wikipedia](https://en.wikipedia.org/wiki/Gas_Mark) This is still standard for gas ovens in the UK, yes. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [March 29, 2016, 7:24pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/13 "2016-03-29T19:24:06Z")
> [@gazpacho](#): > > I was under the impression that this used to be very common in England. You would see recipes with gas setting 7 or similar for setting the oven temperature. > > [Gas mark - Wikipedia](https://en.wikipedia.org/wiki/Gas_Mark) Hell, when I lived in Budapest for a number of years, all my ovens just had two settings: I and II. I was actually surprised at how quickly I learned to cook with it (and that time of my life is really when I learned 80% of what I know on how to cook and bake.) ETA: [Actually, here’s a pretty close picture](http://www.jofogas.hu/pest/Regi_gaz_tuzhely_41650438.htm) of what I had in all three flats I lived in. ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [March 29, 2016, 7:49pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/14 "2016-03-29T19:49:12Z")
> [@leahcim](#): > > My sister used to have an oven with the dials just labelled with the numbers from 1 through 10 with no “real temperature” calibration. Apparently the oven was made by a company that also sold baking ingredients and recipe books that would just use the numbers instead of temperatures, and then that company went out of business. I had an apartment with, I think, the original gas oven in it. It was a really cheap cold-water walk-up with no bathroom (I shared two with the rest of the people on my hall). I had to light this oven with a match, and it just had notches on the dial, no numbers of any sort. No broil. I just guessed that the highest setting was 500’F, the middle was therefore 250’F, etc. It worked pretty well. I could bake a cake and a quiche and a loaf of bread, so it was all good. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [March 29, 2016, 8:00pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/15 "2016-03-29T20:00:31Z")
Calibrate the thermocouple with boiling water. Adjust for air pressure. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [March 29, 2016, 8:07pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/16 "2016-03-29T20:07:25Z")
I bought a leave-in probe-type thermometer a few years ago that I calibrated using a pot of boiling water and a second pot containing an ice-water bath. But I’m not sure whether knowing that the device is accurate at 32 and 212 degrees Fahrenheit tells me anything about its accuracy in the 300-400 degree range. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [March 29, 2016, 8:26pm UTC](https://boards.straightdope.com/t/nothing-accurate-about-calibrating-an-ovens-temperature-arrrgg/750531/17 "2016-03-29T20:26:29Z")
> [@Dewey\_Finn](#): > > I bought a leave-in probe-type thermometer a few years ago that I calibrated using a pot of boiling water and a second pot containing an ice-water bath. But I’m not sure whether knowing that the device is accurate at 32 and 212 degrees Fahrenheit tells me anything about its accuracy in the 300-400 degree range. Sometimes the error is skewed. Refractometers are usually calibrated at the density they are expected to encounter.