Last updated: · Maintained by Lee Harsh (Full-Stack Developer)
A UK Fan (convection) oven circulates hot air across the baking tin, increasing convective heat transfer so you set the dial 20°C lower than a Conventional (static) oven: Fan °C = Conventional °C − 20. For British Gas Marks 1 through 9, Gas Mark 1 equals 135°C (275°F) and each additional Gas Mark adds 14°C (25°F). On a cast-iron AGA range, map 200°C–230°C recipes to the Roasting Oven and 160°C–190°C cakes to the Baking Oven.
Worked Example: Baking a lasagne or tray of roast potatoes written for 200°C Conventional (400°F / Gas Mark 6) converts to 180°C in a UK Fan oven, or goes onto the 3rd or 4th runner of the AGA Roasting Oven for 30–35 minutes (sliding the Cold Plain Shelf above if the cheese browns before the center bubbles).
| Conventional Oven (°C / °F) | UK Fan Oven (-20°C) | British Gas Mark | 4-Oven AGA Placement | 2-Oven AGA Placement (with Cold Shelf) |
|---|---|---|---|---|
| 220°C / 425°F (Scones, Yorkshire Puddings) | 200°C Fan | Gas Mark 7 | Roasting Oven · 2nd or 3rd Runner | Roasting Oven · 2nd or 3rd Runner |
| 200°C / 400°F (Pastry Tarts, Baked Lasagne) | 180°C Fan | Gas Mark 6 | Roasting Oven · 4th Runner | Roasting Oven · 4th Runner + Cold Shelf |
| 180°C / 350°F (Sandwich Sponges, Cookies) | 160°C Fan | Gas Mark 4 | Baking Oven · 3rd Runner | Roasting Oven · 4th Runner + Cold Shelf on 2nd |
| 160°C–165°C / 320°F–325°F (2lb Loaf, Braises) | 140°C–145°C Fan | Gas Mark 3 | Baking Oven · 4th Runner | Roasting Oven · Grid Shelf on Floor + Cold Shelf |
| 110°C–120°C / 230°F–250°F (Pavlova, Meringues) | 90°C–100°C Fan | Gas Mark 1/4–1/2 | Simmering Oven · Middle Runner | Simmering Oven · Middle Runner |
In a Conventional (static) electric or gas oven, natural thermal buoyancy creates a protective stagnant boundary layer of cooler air around your baking tin. Switching on a UK Fan (convection) oven blows heated air across the tin at 1 to 2 metres per second, stripping away that insulating air film and accelerating convective heat transfer into the food.
To prevent cake edges from setting too fast and cracking, set a UK Fan oven exactly 20°C (35°F) lower than the Conventional temperature stated in a recipe: Fan °C = Conventional °C − 20 (so 180°C Conventional becomes 160°C Fan, and 200°C Conventional becomes 180°C Fan).
Converting between American Fahrenheit recipes and British Celsius or Gas Mark dials follows two linear equations: Fahrenheit (°F) = (Conventional °C × 1.8) + 32, and for British Gas Marks 1 through 9, Gas Mark = ((Conventional °C − 135) ÷ 14) + 1. Gas Mark 1 starts at 135°C (275°F), and each full Gas Mark step adds 14°C (25°F).
For quick kitchen reference: Gas Mark 1/4–1/2 (110°C–120°C / 230°F–250°F, 90°C–100°C Fan) dries crisp pavlovas and meringues; Gas Mark 3 (160°C–165°C / 320°F–325°F, 140°C–145°C Fan) bakes rich fruit cakes and 2lb loaves; Gas Mark 4 (180°C / 350°F, 160°C Fan) bakes sandwich sponges and cookies; Gas Mark 6 (200°C / 400°F, 180°C Fan) bakes pastry tarts and lasagne; and Gas Mark 7 (220°C / 425°F, 200°C Fan) bakes scones and Yorkshire puddings.
Unlike thermostat-cycled Fan ovens, a traditional cast-iron AGA range stores thermal energy in heavy iron barrels and transfers heat primarily by multi-directional black-body radiation from the roof, floor, and walls. Because radiant heat does not blow moisture off food surfaces, meats roast with less shrinkage and sponges develop a tender crust.
On a 4-oven AGA, map 200°C–230°C (Gas Mark 6–8) recipes to the Roasting Oven, 160°C–190°C (Gas Mark 3–5) cakes and biscuits to the Baking Oven, and 100°C–140°C casseroles and meringues to the Simmering Oven.
On a 2-oven AGA (which has only a Roasting Oven and a Simmering Oven), you create a moderate 'Baking Oven' zone inside the hot Roasting Oven by sliding the heavy steel Cold Plain Shelf onto the 2nd runner directly above your cake tin on the 4th runner (or grid shelf on the oven floor).
The Cold Plain Shelf blocks downward radiant heat from the cast-iron roof, allowing a Victoria sponge, lasagne, or traybake to cook evenly at an effective 180°C without scorching the top before the middle rises.
Domestic electric and gas oven thermostats frequently drift by 10°C to 15°C over years of use: hang an inexpensive stainless-steel dial thermometer or probe clip in the center of your middle shelf to verify whether your 160°C Fan setting actually holds 160°C. On a cast-iron AGA range, keep oven doors open for as few seconds as possible when loading trays so stored radiant heat in the iron barrel stays balanced for the next course.
All Celsius, Fahrenheit, British Gas Mark 1–9, and cast-iron runner conversions on this page are independent thermodynamics references with no corporate tie to AGA Rangemaster.
Subtract 20°C (35°F) from the Conventional oven temperature: Fan °C = Conventional °C − 20 (for example, 180°C Conventional / 350°F / Gas Mark 4 converts to 160°C Fan, and 200°C Conventional / 400°F / Gas Mark 6 converts to 180°C Fan).
Gas Mark 1 equals 135°C (275°F), and each full Gas Mark step adds 14°C (25°F): Gas Mark = ((Conventional °C − 135) ÷ 14) + 1. Thus 165°C (325°F) is Gas Mark 3, 180°C (350°F) is Gas Mark 4, 200°C (400°F) is Gas Mark 6, and 220°C (425°F) is Gas Mark 7.
On a 4-oven AGA, use the Roasting Oven for high-heat 200°C–230°C bakes (Yorkshire puddings, scones, roast potatoes, lasagne), the Baking Oven for moderate 160°C–190°C sponges and cookies, and the Simmering Oven for 100°C–140°C meringues and slow braises.
Place your cake tin or lasagne dish on the 4th runner of the Roasting Oven and slide the heavy steel Cold Plain Shelf onto the 2nd runner directly above it to shield the top from intense downward cast-iron radiation.
A cast-iron AGA heats food via multi-directional radiant heat from its iron walls rather than blowing dry forced air across the food surface, preserving surface moisture while browning evenly.
No—all temperature conversion formulas and runner guides on this page are independent kitchen thermodynamics references and are not affiliated with AGA Rangemaster or any named chef.
Explore our 7 core culinary and nutrition calculators, 18 archetype scaling hubs, and primary scientific reference databases:
Static food blogs lock every recipe to a single yield, a single cake tin size, and a single oven type—leaving you to guess when converting an 8-inch sponge to a 2lb loaf tin, boiling blackberry jam to 105°C, or smoking Famous Dave's ribs at 225°F.
Our deterministic calculator applies verified UK/US gram densities, pan surface-area ratios, AGA/Smoker/Slow Cooker offsets, and Mary Berry All-in-One method simplifications automatically in one place.
Scale your ingredients, convert cake tins and appliances, and export your recipe checklist with confidence.
Start Scaling & Converting