Fan oven
An oven circulating hot air with a fan, giving faster and more even heat transfer than a static oven at the same setting.
Also called what temperature is a slow oven (UK); what temperature is a moderately slow oven (UK); what temperature is a medium fan oven (UK); celsius to fahrenheit baking chart (INTERNATIONAL); oven temperature descriptions (UK); convection oven (US); fan oven symbol (UK); moderate oven (UK); fan oven temperature (UK); fan-assisted oven (UK) — Sometimes distinguished from a true fan oven, which has a heating element around the fan itself.
A fan circulates air inside the oven cavity, which increases the rate of heat transfer to the food and evens out the temperature differences a static oven always has.
The practical consequence is that a fan oven at a given dial setting bakes faster and browns more than a static oven at the same setting. The usual convention is to reduce the set temperature by around twenty degrees Celsius, or to shorten the time.
That convention is a rule of thumb rather than a physical constant. It varies by oven and by product, and it works less well for delicate items where the moving air can skin a surface before the interior has risen.
What it changes
- Increases browning. Faster heat transfer and moving air drive surface drying and browning reactions harder.
- Changes volume. A surface that sets earlier can restrict expansion in delicate bakes.
Optional — convenience rather than capability
Circulating hot air for faster, more even heat transfer.
What works instead
A static oven does everything a fan oven does, more slowly and less evenly. The most valuable accessory for either is an oven thermometer: domestic ovens routinely run some way from their dial setting, and that discrepancy causes more faults than the fan does.
The gas mark scale, and its Celsius equivalents
Gas marks are a British scale with no international equivalent, and recipes that use them frequently give no conversion.\n\nThe conventional readings are: gas mark 1 is about 140 °C, 2 about 150, 3 about 170, 4 about 180, 5 about 190, 6 about 200, 7 about 220, 8 about 230 and 9 about 240. Gas mark 10 appears on some ovens and is around 260. Below 1 there are usually marks S, 1/4 and 1/2, running from roughly 110 to 130 °C.\n\nThese are conventions rather than definitions. The scale is a set of positions on a valve, not a set of temperatures, and manufacturers differ. Older recipes are also written for ovens that were less accurate than modern ones, so a conversion that looks precise is carrying an imprecision from both ends.\n\nFor a fan oven, apply the usual reduction to the converted Celsius figure rather than to the gas mark. Gas ovens are not fan ovens, so the two adjustments are separate steps and applying both to the same number is a common error.
Which setting for which bake
The fan is not better or worse; it does one thing and that thing suits some bakes and not others.\n\nUSE THE FAN for anything baked in quantity across several shelves, for biscuits and pastry where drying the surface is wanted, and for roasting. Evenness and multi-shelf capacity are the reasons the setting exists.\n\nPREFER STATIC HEAT for delicate sponges, soufflés, meringues and baked custards — anything where a skin forming early is the failure mode. Moving air dries a surface, and a surface that sets before the interior has finished rising restricts the rise.\n\nFOR BREAD the answer depends on the loaf. A fan helps crust formation and colour late in the bake and works against the humid start a lean loaf wants, which is why a lidded pot and a fan setting are often used together — the pot supplies the humidity the fan is removing.\n\nFOR PIZZA use the hottest setting the oven has, fan included. Domestic ovens are far below the temperatures pizza is designed around, so every degree helps.
What the dial actually tells you
The fan symbol is a small fan or propeller, usually inside a square. Where an oven has both fan and conventional settings, the fan symbol may appear alone or with a horizontal bar above or below it — the bars indicate which elements are on, so a fan symbol with a top and bottom bar is fan-assisted rather than true fan.
Manufacturers are not consistent about this, and the manual is a better authority than any general guide. What is consistent is the direction: a setting with a fan symbol moves air, and moving air transfers heat faster than still air at the same temperature.
"Moderate", "low" and "hot" — and why they are vaguer than they look
Older recipes describe an oven rather than a number. The conventional readings are roughly: low or cool around 150 °C, moderate around 180 °C, moderately hot around 190 °C, hot around 220 °C, very hot above that.
These are conventions rather than definitions, and they refer to CONVENTIONAL oven temperatures. For a fan oven the usual guidance is to reduce by about 20 °C — so a moderate fan oven is commonly taken as about 160 °C.
Both of those are rules of thumb. The reduction depends on the oven, and domestic ovens routinely run some way from their dial in the first place. A moderate oven is a description of what the bake needs, not a specification, and an oven thermometer answers the question the dial cannot.
Related
Apply this with a tool
The fan adjustment is the conversion readers most often need, and the page explains why it is a convention rather than a constant.
Compared in
The equipment record carries the symbols, the gas mark scale and the per-product guidance; the comparison carries the argument.