Today I’m writing about an extremely serious subject, oven temperature conversion. I hope you’re sitting comfortably because this is a seriously hot topic. Badum-tish.
Converting oven temperatures accurately
OK, I promise, no more awful jokes.
Sometimes, we need all the help we can get when it comes to cooking a new recipe. Like when you’ve worked and fretted for hours before cutting into a cake, only to find the base is STILL soggy despite an extra 30 minutes in the oven. Or those roasted vegetables that simply WON’T BROWN LIKE IN THE PHOTO. And we’ve all had something, errr, how do I put it, ‘caramelise’ a bit more than intended.
Some of these situations are completely avoidable. And I want to help you with these problems through the simple process of accurate oven temperature conversions, because the internet is full of incorrect information, and you might have been using that false information. Even some people who write the recipes might be using the wrong information.
Some of the top Google search results for ‘oven temperatures conversion’ have misleading, or simply wrong figures that are up to 10% out in some cases. That inaccurate information is not helping anyone, it’s just lazy, unchecked content. So by using the tables below, or the handy free PDF download that I’ve created, you can give yourself a head start next time. Sometimes a few small changes to the way you work can have a much bigger, cumulative effect on the outcomes.
Going back a few hundred years, an oven was a brick or stone enclosure, with a fire in it. Lots of different materials would be burned fiercely to generate heat, heating the surrounding stone of the oven. Once the fire had burned out, the embers and ash would be removed, clearing the way for the food to be put into the oven and cooked.
The oven temperature was uncontrolled, determined only by the amount of heat stored in the stone. If the fire hadn’t been strong enough, then the oven wouldn’t be very hot. If the fire had burned intensely for a long time, then the oven would be extremely hot. Also, as the stone cooled down, the temperature of the oven would come down. This whole process gave the cook very little control over the oven temperature. It’s temperature would have been judged largely by guesswork, either from the feel of the heat, or by throwing flour on the floor of the oven; if it browned too quickly then the oven was too hot.
But with the industrial revolution in the 1800s, a public gas network was created which gave a reliable supply of gas to people all over the country. Gas stoves were being developed and people started having them in their homes. These ovens had no temperature scale and were controlled simply by adjusting the gas inlet.
Then in the 1920s, a gas thermostat called the ‘Regulo’ was invented, which was a way of controlling the temperature of a gas oven. This was the forebear to the Gas Mark scale from 1 to 9 which we’re now familiar with. These units came about when the UK was using Fahrenheit as it’s unit of measurement for heat, so understandably, the Gas Mark range relates directly to 25º increments of Fahrenheit (see table 1, below).
The problem is when people start converting these temperatures backwards and forwards, as rounding errors start to creep in and they just get the sums wrong. Or, they simply round the numbers up or down loads, as if we, the great cooking public are unable to understand numbers that aren’t rounded to the nearest 10. Duh.
Although your modern oven will have a temperature gauge on it, that doesn’t mean you can trust it. There are very few accurate domestic ovens out there, so it’s good practice to use a good quality oven thermometer (affiliate link) to check your temperatures.
Fan ovens circulate the heat much more efficiently around the food, so require a lower temperature than non-fan ovens. The general rule is to reduce the temperature by 20ºC, 36ºF, for a fan oven, although your oven instructions (if you still have them!) might have some more information specific to that product.
to check your temperatures.