Oven temperatures, and the digit that means three different ovens

Set an oven to 4 and you get 120 C in a French recipe, 180 in a British one and 200 in a German one. That is an 80 degree spread on a single digit, and none of the three scales prints a unit, so nothing on the page tells you which one you are reading.

The collision, side by side

Tabulating the three together is not the rare part. CooksInfo has published a combined grid since 2007, and it disagrees with this one: it pairs a British gas mark 4 with Stufe 2, where our German source puts Stufe 4 at 200 C. Two tables, both citing their sources, and a German column that does not survive the comparison. That is the finding worth carrying, and it is the reason the spread in the line above is ours rather than the world's.

Read a German Stufe 4 as a British gas mark and the oven runs 20 degrees cold. Read a French thermostat 4 as a gas mark and it runs 60 degrees hot. The one pairing that does line up is a British gas mark 4 against a French thermostat 6, both 180 C, which is a coincidence rather than a correspondence and is worth knowing precisely so you do not generalise from it.

The French scale computes, and the rule is a rounding

The thermostat looks like the most arbitrary of the three to an English speaker, a bare number with no unit and no history anyone remembers. It is the one you can do in your head. The mark times 30 gives the temperature in Celsius, and across the 10 marks our source prints it holds exactly: 1 is 30 C, 6 is 180, 10 is 300. You do not need the table, only the multiplication.

Two things stop that from making the thermostat the exact scale. The rule is a rounding, and it is not even a French one. French Wikipedia traces the steps to increments of 50 degrees Fahrenheit, 27.78 C apiece, rounded up to a comfortable 30: the tidiest scale in the kitchen is an American ladder with the corners taken off. And the published French tables do not agree with each other. Petit Larousse de la cuisine puts thermostat 1 at 100 to 120 C and thermostat 6 at 200 to 220. Ginette Mathiot, in Je sais cuisiner, gives 105 to 140 for thermostats 1 and 2 and 205 to 225 for 6 and 7. The same article says it in as many words: the corresponding temperatures vary according to the cookery book and do not always follow a simple mathematical law. So the multiplication is real and it is a convention, which is exactly what we say about the other two.

The other two are conventions, and one says so itself

The German Stufe is not a standard. Gutekueche, the source we take the values from, prints them as rough guidelines that vary from appliance to appliance and maker to maker, which is a caveat worth carrying rather than quietly dropping. We record it in our data as an unstandardised scale, alongside the British gas mark. So of the three national scales in this page, the ones an English speaker treats as solid (German gas oven setting and British gas mark) are the loose ones, and the one that looks like a foreign quirk is the one that computes.

There is more than one Stufe table in circulation, and this is the column to distrust. Ours comes from Gutekueche, where Stufe 3 is 180 C and Stufe 4 is 200. CooksInfo reaches 180 C a whole rung earlier, at Stufe 2, where our ladder still reads 160, and then prints 210 C at Stufe 3, a temperature our ladder never lands on at all. Neither cites a standards body, because there is not one to cite. The 80 degree headline at the top of this page is computed from our table, so read it as the size of the trap on the numbers we publish rather than a figure every German chart would agree with.

For the British scale we record only the two marks that make the trap, and we take them from a British kitchen rather than from a conversion aggregator, because a scale is best quoted from the country that uses it. Gas mark 6 is 200 C on the strength of nigella.com, which prints every recipe as degrees centigrade, fan, gas mark and Fahrenheit together, states that the four figures given are equivalent, and adds the detail an aggregator would never carry: gas marks used to be common in Britain and are now used less, kept on the site because readers asked for them.

Fan ovens take about twenty degrees off

German recipes routinely print two settings, Ober- und Unterhitze for conventional heat and Umluft for the fan, and the fan figure sits about 20 C lower. The reason is circulation rather than power: moving air carries heat to the food faster, so the same browning happens at a lower reading. Manufacturers differ, and an oven thermometer settles it better than any chart, which is the same argument our methodology page makes about scales and cups.

Why there is no full gas mark table here

Every cooking site in the English language carries the gas mark ladder from 1 to 9, and reproducing it would add nothing except another copy to disagree with the others. We record the two marks that make the collision, and we take both from a British kitchen rather than from a conversion aggregator, because a scale should be quoted from the country that uses it. That is the same rule that keeps us from filing a generic oil weight as olive oil or a granular brown sugar as the moist packed kind. If you want the full British ladder, any British cookery site has it, and they agree with each other on it.

Reading a bare number, in practice

Work out the country before the temperature. A recipe in Celsius with a number beside it in brackets is British or Australian and the bracketed figure is the gas mark. A recipe that says thermostat, or th., is French, and you can multiply by 30 without looking anything up. A recipe that says Stufe is German or Austrian, and it is the one case where the scale itself carries a warning: the values shift by appliance, so treat the table as a starting point and let the food tell you the rest. When a recipe gives no clue at all, the safest reading is the middle of the three, since being 40 degrees hot spoils a bake faster than being 20 degrees cold.

An oven thermometer settles all of this for the price of a bag of flour, and it also catches the other thing no chart can: ovens drift from their own dials. That is the same argument for a kitchen scale that runs through this site, applied to heat instead of weight.

Questions about oven scales

What is thermostat 6 in Celsius?

180 C. The French scale is a rule rather than a lookup: the thermostat number times 30 gives the temperature. That is also where it collides with the British gas mark 6, which is 200 C.

Is Stufe the same as gas mark?

No, and this is the one worth checking twice. Stufe 4 is 200 C while gas mark 4 is 180 C. The German scale is also the loosest of the three: its own publisher calls the values guidelines that vary by appliance and maker.

How much do I drop the temperature for a fan oven?

About 20 C below the conventional setting, the offset German recipes assume when they print Umluft beside Ober- und Unterhitze. Manufacturers vary, so treat it as a starting point and watch the bake.

Two more things a foreign recipe assumes: the size of its eggs, on egg sizes, and the yeast that raises it, on the yeast converter, and the Stufe scale in the context of a whole German recipe is on German recipe measurements, the thermostat in a whole French one on French recipe measurements, and every foreign-recipe guide on the world measures hub.

Sources

Gutekueche for the German Stufe values and for the statement that they are appliance-dependent guidelines. Bricolage for the French thermostat scale and its times-30 rule. Nigella.com for the British gas mark figures, in the form its own recipes print them. CooksInfo for the rival Stufe ladder, and French Wikipedia for the origin of the 30 and for the two cookery books that disagree about it. Full citations on the sources page.